LU-11415 socklnd: improve scheduling algorithm

LU-11415 socklnd: improve scheduling algorithm

Modified the scheduling algorithm to use all scheduler threads
available. Previously a connection is assigned a single thread
and can only use that one. With this patch any scheduler thread
available on the assigned CPT can pick up and work on requests
queued on the connection.

Lustre-change: https://review.whamcloud.com/33740
Lustre-commit: 89df5e712ffd40064f1d4ce2f00f9156f68a2262

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I7e8e5220e1914155fd793994485e3a443fe1ba44
Reviewed-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34299
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>