Skip sqlite-specific tests if sqlite is not configured

There are several tests in test_migration_utils which only work if
sqlite is configured for migration tests, but two of them are missing
the conditional checks for skipping the test.

Also renames test_check_shadow_table_with_unsupported_type to
test_check_shadow_table_with_unsupported_sqlite_type since it's specific
to sqlite.

Closes-Bug: #1275352

Change-Id: I46f1b95e654bc702c76790350a8929d03c04e0a1
Merge "Skip sqlite-specific tests if sqlite is not configured"