libadmin: Don't double check for required param

The server, process and stat_type parameters are declared as
required when the command syntax is set up - so they must be
present when the command handler is called. So, don't bother
checking for them.

Caught by coverity (#985963, #985964, #985965, #985966, #985967,
		    #985968, #985969, #985970, #985971, #985972,
		    #985973, #985974, #985975, #985976, #985977)

Change-Id: Ic0565aa50c5a998b327efe60d460a182a93c7552
Reviewed-on: http://gerrit.openafs.org/9399
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>