usermerge role: give usermerge right to default user
usermerge role: give usermerge right to default user

Change-Id: Ic409085777346e79beb6047dcec30aa67611361e

wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant