bump variance on test_merge_load
bump variance on test_merge_load

This test is very sensitive and fluctuates a lot, failing builds,
bump the variance to try and resolve.

Change-Id: Ia19bb8871b432059cb3917ca0050a68f75c0a0f2

zzzeek/sqlalchemy,monetate/sqlalchemy,j5int/sqlalchemy,j5int/sqlalchemy,monetate/sqlalchemy,graingert/sqlalchemy,graingert/sqlalchemy,sqlalchemy/sqlalchemy