mediawiki: /usr/local/apache/common-local => /srv/mediawiki

Update file paths to point to /srv/mediawiki instead of
/usr/local/apache/common{-local} in wmerrors.ini and the configs for the
snapshots and the deployment config.

Change-Id: Ic03360cd808f1f9aff2cde606b3e28ce65dc4b6b
Merge "mediawiki: /usr/local/apache/common-local => /srv/mediawiki" into production