Apply missing MySQL test-database patches from 90 to 93

Created by: mkszuba

Description

Since Ensembl Core version 91 the test databases test_db_homo_sapiens_variation, test_db_mus_musculus_variation and test_db_multi_compara have been stuck at schema version 90 due to what seems to have been an incomplete patching of databases (in all three cases only patch b was applied). This PR brings these three databases into sync with the rest.

Nb. this should probably be merged into master as well.

Use case

Running the Core test suite when the software and the database-schema version do not match could result in unexpected failures; fortunately so far all these three databases being stuck at 90 did was produce warnings. Moreover, the incomplete application of schema version 91 has since prevented operation of patch_test_database.pl in fixlast mode.

Benefits

Eliminates incompatibility between software and database-schema version in the test suite, gets fixlast mode of patch_test_database.pl working again.

Possible Drawbacks

None I can think of.

Testing

Have you added/modified unit tests to test the changes?

No (not applicable?).

Have you run the entire test suite and no regression was detected?

I have run the entire test suite with this commit merged into both current master (no errors; the incompatibility warnings are of course still present because the master core version is 94) and the current release/93 (no new errors).