fix travis check style for Go

[helinwang]

Go pre-commit hook does not modify code, so git diff --exit-code will have 0 exit code in that case.

[wangkuiyi]

Travis CI complains that it cannot find golint.

CRLF end-lines remover...............................(no files to check)Skipped
yapf.....................................................................Passed
Check for added large files..............................................Passed
Check for merge conflicts................................................Passed
Check for broken symlinks................................................Passed
Detect Private Key...................................(no files to check)Skipped
Fix End of Files.........................................................Passed
clang-formater...........................................................Passed
go fmt...................................................................Passed
go lint..................................................................Failed
hookid: go-lint
/home/travis/.pre-commit/repony4WjS/run-go-lint.sh: line 9: golint: command not found

[helinwang]

@wangkuiyi Thanks for pointing out! #2885 fixes it, I will rebase the fix after that gets merged.

[gongweibao]

LGTM++