check if user key already exists
Call upgrade script for 5.6.3.1

The upgrade script for concrete5 5.6.3.1 is defined but is not called by
the upgrade script. Let's call it...
Merge pull request #1763 from Remo/patch-3

check if user key already exists
Merge pull request #1765 from mlocati/call-5631-upgrade-script

Call upgrade script for 5.6.3.1