Fix test.sh to run on mac.

The find command errors on Mac. This uses "go list", which should
be easier to maintain going forward.

Also switch to one "go test" execution with many paths. This lets
go test parallelize more effectively, and cuts the runtime down
from 2.5m to 1.5m on my workstation.

test.sh

@@ -16,11 +16,10 @@ set -e
 
 REPO_PATH="k8s.io/minikube"
 
-# Run all test files.
-for TEST in $(find -name "*.go" | grep -v vendor | grep -v integration | grep _test.go | grep -v go-bindata | cut -d/ -f2- | sed 's|/\w*.go||g' | uniq); do
-  echo $TEST
-  go test -v ${REPO_PATH}/${TEST}
-done
+# Run "go test" on packages that have test files.
+cd ${GOPATH}/src/${REPO_PATH}
+TESTS=$(go list -f '{{ if .TestGoFiles }} {{.ImportPath}} {{end}}' ./...)
+go test -v ${TESTS}
 
 # Check gofmt
 diff -u <(echo -n) <(gofmt -l -s . | grep -v "vendor\|\.gopath\|localkubecontents.go")