cdr_pgsql: Fix CLI "cdr show pgsql status" command.

The command always showed the usage information.

* Fix the error in command validation for CLI_SHOWUSAGE.

ASTERISK-24959 #close
Reported by: Rodrigo Ramirez Norambuena

Change-Id: I584f0936bb01001336a468a55c1d05d79fe795d5