Merge pull request #68939 from aainscow/zero_sized_object

test/osd: Fix event loop context violations in test fixtures

Reviewed-by: Bill Scales <bill_scales@uk.ibm.com>

diff --cc src/test/osd/PGBackendTestFixture.cc
Simple merge

diff --cc src/test/osd/PGBackendTestFixture.h
Simple merge

diff --cc src/test/osd/TestECFailoverWithPeering.cc
Simple merge