CarrierConfigRule#setHoldCarrierPrivilege will try to acquire/drop the
carrier privilege, but does not wait for the result of the operation. If
a test immediately calls an API that requires carrier privilege before
the operation completes, then it will fail.
Fix this by waiting for the operation to succeed before returning.
Bug: 295979433
Test: presubmit
Change-Id: Ic7cc9e1dbc206fbc0c3b79058b5782d93e89f1d7
d3058d5ffe