Make test_nvp_sync.SyncLoopingCallTestCase reliable
Make test_nvp_sync.SyncLoopingCallTestCase reliable

This patch removes the previous check that verified the mocked
looping call had an exact number of calls, and replaces it with a
simpler check that just verifies that the mock has been called.

As a consequence, this patch also shortens the test duration.

Closes-Bug: 1241969

Change-Id: Ia7bc66e1f2f631e46ddcbe0eacc1d5b2481274cb

gkotton/vmware-nsx,gkotton/vmware-nsx