Tests: applyOps_c_renameCollection_twoDbs and renameCollection_twoDbs both make use of the `movePrimary` command which is available on mongos only, but do not specify `skipUnlessSharded`.  It's unclear which resolution is prefered.

1. Ignore CommandUnknown error.  This is the current state, if desired we should explicitly comment that failure is an option.
2. Specify `skipUnlessSharded: true` if this is in deed a mongos only test.