Update unit-test && e2e to run on Mac

[yeahdongcn]

I encountered several issues in make controller-gen, make unit-test, make e2e on Mac.

Please see the detailed error message here:

• make controller-gen

  ➜ volcano (master) make controller-gen                       
  go: creating new go.mod: module tmp
  go: cannot install cross-compiled binaries when GOBIN is set
  make: *** [controller-gen] Error 1

• make unit-test

  ➜ volcano (master) make unit-test
  go clean -testcache
  if [ Darwin = 'Darwin' ];then\
                  GOOS=darwin go list ./... | grep -v "/e2e" | xargs  go test;\
          else\
                  go test -p 8 -race $(find pkg cmd -type f -name '*_test.go' | sed -r 's|/[^/]+$||' | sort | uniq | sed "s|^|volcano.sh/volcano/|");\
          fi;
  ?       volcano.sh/volcano/cmd/cli      [no test files]
  ...
  ?       volcano.sh/volcano/example/kubecon-2019-china/scripts   [no test files]
  fork/exec /var/folders/p9/dbq3q88x7c39y7tmwqgj6yjr0000gn/T/go-build3785830628/b889/options.test: exec format error
  FAIL    volcano.sh/volcano/cmd/controller-manager/app/options   0.001s
  fork/exec /var/folders/p9/dbq3q88x7c39y7tmwqgj6yjr0000gn/T/go-build3785830628/b1041/options.test: exec format error
  FAIL    volcano.sh/volcano/cmd/scheduler/app/options    0.002s

This is because GOOS ?= linux is explicitly set in Makefile and consumed in making docker images, etc.

So I slightly update the OS env and access it whenever needed (e.g. go test/install, ginkgo) and everything works perfectly on Mac && Linux.

Testing done (on both Mac && Linux):

1. make vcctl -> ok
2. make unit-test -> ok
3. make controller-gen -> ok
4. make mirror-licenses -> ok
5. make generate-code -> ok
6. make e2e-test-jobp -> ok

[volcano-sh-bot]

Welcome @yeahdongcn!

It looks like this is your first PR to volcano-sh/volcano.

Thank you, and welcome to Volcano. 😃

[shinytang6]

/lgtm

[shinytang6]

cc @Monokaix @hwdef @william-wang

[lowang-bh]

fixes #2894

[yeahdongcn]

Code rebase from upstream/master.

[hwdef]

/lgtm

[Monokaix]

/lgtm

[william-wang]

/approve

[volcano-sh-bot]

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