www-misc/mozilla-sync-server-storage: Use REQUIRED_USE for ldap/memcached/mysql/sqlite.
www-misc/mozilla-sync-server-full: Use REQUIRED_USE for ldap/memcached/mysql/sqlite.
www-misc/mozilla-sync-server-full: Don't install all config files unconditionally.
www-misc/mozilla-sync-server-full: Remove test from IUSE.