Postgres updater fixes to make update.php able to run
* Remove redundant schema prefix from relname=x query. The
schema filtering is already done via the JOIN. The relname
portion is just the table name not <schema>.<table name>.
* Avoid explicit table schema qualification and rely on the
search path, as MW 1.27 did. Previously it only used the
global $wgDBschema var to pass to determineCoreSchema()
instead of keeping it in mSchema.
* Clean up some code duplication in Database::tableName() and
make the code comments clearer.
* Make DatabasePostgres::tableName() use parent::tableName()
instead of a method that just wraps this method. The intent
seems clearer this way.
* Remove unused return value in
PostgresUpdater::rebuildTextSearch().
Bug: T148628
Change-Id: Id11d9576b7c2fdad22ff7f90727c12997217a632