test/librados/aio.cc: silence coverity with scope_guard
Fix for:
CID
1313405 (#1 of 1): Resource leak (RESOURCE_LEAK)
leaked_storage: Variable my_completion2 going out of scope
leaks the storage it points to.
CID
1219522 (#1 of 1): Resource leak (RESOURCE_LEAK)
leaked_storage: Variable my_completion going out of scope
leaks the storage it points to.
CID
1219501 (#1 of 1): Resource leak (RESOURCE_LEAK)
leaked_storage: Variable my_completion going out of scope
leaks the storage it points to.
CID
1313406 (#1 of 1): Resource leak (RESOURCE_LEAK)
leaked_storage: Variable my_completion2 going out of scope
leaks the storage it points to.
Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>