Test Suite error - time.Local vs time.UTC?

Seeing some failures for make testsuite for libbeat, that seem to be Timezone related. (My computer is in US Eastern.)

command [go test -cover -coverprofile /tmp/gotestcover-1560318489 github.com/elastic/beats/v7/libbeat/common/fmtstr]: exit status 1
--- FAIL: TestEventFormatString (0.00s)
    formatevents_test.go:135: test(0): empty string
    formatevents_test.go:135: test(1): no fields configured
    formatevents_test.go:135: test(2): expand event field
    formatevents_test.go:135: test(3): expand with default
    formatevents_test.go:135: test(4): expand nested event field
    formatevents_test.go:135: test(5): expand nested event field (alt. syntax)
    formatevents_test.go:135: test(6): multiple event fields
    formatevents_test.go:135: test(7): same fields
    formatevents_test.go:135: test(8): same fields with default (first)
    formatevents_test.go:135: test(9): same fields with default (second)
    formatevents_test.go:135: test(10): test timestamp formatter
    formatevents_test.go:135: test(11): test timestamp formatter
    formatevents_test.go:146: 
        	Error Trace:	formatevents_test.go:146
        	Error:      	Not equal: 
        	            	expected: "2015-05-01T20:12:34.000Z: 2015.05.01"
        	            	actual  : "2015-05-02T00:12:34.000Z: 2015.05.01"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1 @@
        	            	-2015-05-01T20:12:34.000Z: 2015.05.01
        	            	+2015-05-02T00:12:34.000Z: 2015.05.01
        	Test:       	TestEventFormatString
--- FAIL: TestTimestampFormatString (0.00s)
    formattimestamp_test.go:89: test(0): empty string
    formattimestamp_test.go:89: test(1): no fields configured
    formattimestamp_test.go:89: test(2): expand field
    formattimestamp_test.go:89: test(3): expand with default
    formattimestamp_test.go:89: test(4): expand nested field
    formattimestamp_test.go:89: test(5): test timestamp formatter
    formattimestamp_test.go:89: test(6): test timestamp formatter
    formattimestamp_test.go:106: 
        	Error Trace:	formattimestamp_test.go:106
        	Error:      	Not equal: 
        	            	expected: "2015-05-01T20:12:34.000Z: 2015.05.01"
        	            	actual  : "2015-05-02T00:12:34.000Z: 2015.05.01"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1 @@
        	            	-2015-05-01T20:12:34.000Z: 2015.05.01
        	            	+2015-05-02T00:12:34.000Z: 2015.05.01
        	Test:       	TestTimestampFormatString
FAIL
coverage: 83.9% of statements
FAIL	github.com/elastic/beats/v7/libbeat/common/fmtstr	0.442s
FAIL

and


command [go test -cover -coverprofile /tmp/gotestcover-165778516 github.com/elastic/beats/v7/libbeat/common/fmtstr]: exit status 1
--- FAIL: TestTimestampFormatString (0.00s)
    formattimestamp_test.go:89: test(0): empty string
    formattimestamp_test.go:89: test(1): no fields configured
    formattimestamp_test.go:89: test(2): expand field
    formattimestamp_test.go:89: test(3): expand with default
    formattimestamp_test.go:89: test(4): expand nested field
    formattimestamp_test.go:89: test(5): test timestamp formatter
    formattimestamp_test.go:89: test(6): test timestamp formatter
    formattimestamp_test.go:106: 
        	Error Trace:	formattimestamp_test.go:106
        	Error:      	Not equal: 
        	            	expected: "2015-05-01T20:12:34.000Z: 2015.05.01"
        	            	actual  : "2015-05-02T00:12:34.000Z: 2015.05.01"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1 @@
        	            	-2015-05-01T20:12:34.000Z: 2015.05.01
        	            	+2015-05-02T00:12:34.000Z: 2015.05.01
        	Test:       	TestTimestampFormatString
FAIL
coverage: 83.9% of statements
FAIL	github.com/elastic/beats/v7/libbeat/common/fmtstr	0.327s
FAIL

For all of these errors, the test code is using time.Local, but the comparing to a time that is in UTC. That seems like an error in the test suite? Changing to time.UTC seems to give correct test operation.

I'm happy to make a PR to fix these 4 unit tests. But the contributing guidelines say to create a discussion topic first.