Check "cmd add-role-holder" is executed complete before executing next step.

Because "cmd add-role-holder" only post the job into the handler , and it will not be immediately executed
when there are other jobs queued in handler.
Which causes the case executes the next step before role holder is added, then fails to check permission for test apk.

Fix:
Check "cmd add-role-holder" is executed complete before executing next step.

Tests:
"run cts -m CtsBlobStoreHostTestCases -t com.android.cts.host.blob.BlobStoreMultiUserTest#testBlobAccessAcrossUsers_withAssistRole"

Issue:243880573

Change-Id: I8e8d69e55a195b3614d46206f49744ff2b240452
Merged-In: I8e8d69e55a195b3614d46206f49744ff2b240452
(cherry picked from commit 4fb8dbc6e3928126148cdff013a883ebaf4d1c01)
1 file changed