libcmd: Don't increment array then discard result

libcmd: Don't increment array then discard result

We don't need to increment argv here, as we're about to return
to the caller.

Change-Id: I442fe741e4bda91e12375a6fe72657dc215c4e78
Reviewed-on: http://gerrit.openafs.org/5078
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>