socket: Fixed parsing RPC records containing multi fragments

In __socket_proto_state_machine(), when parsing RPC records containing
multi fragments, just change the state of parsing process, had not
processed the memory to coalesce the multi fragments.

Cherry picked from commit fb6702b7f8ba19333b7ba4af543d908e3f5e1923:
> Change-Id: I5583e578603bd7290814a5d26885b31759c73115
> BUG: 1139598
> Signed-off-by: Gu Feng <flygoast@126.com>
> Reviewed-on: http://review.gluster.org/8662
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Niels de Vos <ndevos@redhat.com>
> Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
> Tested-by: Raghavendra G <rgowdapp@redhat.com>

Change-Id: I5583e578603bd7290814a5d26885b31759c73115
BUG: 1136221
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/8848
Tested-by: Gluster Build System <jenkins@build.gluster.com>