Also make the update() methods of the subclasses use DB_MASTER as they
should. This avoids read-only errors.
In addition, avoid passing a dummy argument of null in some cases
within SearchEngineFactory::create(). Fix some dynamic calls to
static methods too.
Change-Id: Id94f34994b0f9c18e23ef30cb2fe895e6dedd09c
This is more consistent with LoadBalancer, modern, and inclusive
of master/master mysql, NDB cluster, and MariaDB galera cluster.
The old constant is an alias now.
Change-Id: I0b37299ecb439cc446ffbe8c341365d1eef45849
