kern/parser: Fix resource leak if argc == 0

kern/parser: Fix resource leak if argc == 0

After processing the command-line yet arriving at the point where we are
setting argv, we are allocating memory, even if argc == 0, which makes
no sense since we never put anything into the allocated argv.

The solution is to simply return that we've successfully processed the
arguments but that argc == 0, and also ensure that argv is NULL when
we're not allocating anything in it.

There are only 2 callers of this function, and both are handling a zero
value in argc assuming nothing is allocated in argv.

Fixes: CID 96680
Signed-off-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>