extras: Don't update RETVAL with invalid value.

Problem:
Start and restart functions update the value of RETVAL internally.
Assigning $? to RETVAL after function return was updating RETVAL with
invalid value.

Fix:
Removed assignment statement after start and restart functions return.

Stop function was always returning 0 as return value due to one extra echo
command. Removed echo line.

Change-Id: Iec1a83a83463f419dd45e12daf4e5ded80568a3a
BUG: 888442
Signed-off-by: Raghavendra Talur <rtalur@redhat.com>
Reviewed-on: http://review.gluster.org/4349
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>