check_locks patch for proper performance Data

[jwpit]

Hello,

in Version 2.22.0, check_postgres.pl only returns the parameters total,waiting and exclusive in the performance data, if the amount of these Locks is not null. pnp4nagios fails on reading these rrd files. The attached patch ensures, that those parameters are always returned, if they are set in warning or critical. Null is replaced by zero. check_locks.patch.txt