staging/lustre/gss: fix few issues found by Klocwork Insight tool

Array 'message_buf' of size 500 may use index value(s) -1

Object 'enc_key.data' was freed at line 164 after being freed
by calling 'free' at line 150. Also there are 3 similar errors
on line(s) 164.

Suspicious dereference of pointer 'vmsg' before NULL check at
line 187. Also there are 2 similar errors on line(s) 196, 205.

Suspicious dereference of pointer 'rmsg' before NULL check at
line 191. Also there are 2 similar errors on line(s) 200, 209.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/9274
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4629


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>