Run only unit tests for now

This PR disable all other tests except the unit tests until
the snapshot beta API PR is merged.

Author: xing-yang

release-tools/prow.sh

@@ -242,7 +242,9 @@ configvar CSI_PROW_DEP_VERSION v0.5.1 "golang dep version to be used for vendor
 # thus only makes sense in repos which provide their own CSI
 # driver. Repos can enable sanity testing by setting
 # CSI_PROW_TESTS_SANITY=sanity.
-configvar CSI_PROW_TESTS "unit parallel serial parallel-alpha serial-alpha sanity" "tests to run"
+# NOTE(xyang): Run only unit tests until snapshot beta API PR is merged.
+configvar CSI_PROW_TESTS "unit" "tests to run"
+# configvar CSI_PROW_TESTS "unit parallel serial parallel-alpha serial-alpha sanity" "tests to run"
 tests_enabled () {
     local t1 t2
     # We want word-splitting here, so ignore: Quote to prevent word splitting, or split robustly with mapfile or read -a.