Only run pull mirror related queries when `plans` table exists, which means...

Only run pull mirror related queries when `plans` table exists, which means we're running against EE
2 jobs for dm-mirror-check-query in 2 minutes and 16 seconds
Status Job ID Name Coverage
  Test
passed #2454119
rspec

00:02:08

passed #2454120
rubocop

00:02:16