GFS2: Deletion of unnecessary checks before two function calls

The functions iput() and put_pid() test whether their argument is NULL
and then return immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>