Timeout triggers failures running tempest for ZFSSA driver.

Adding a property to setup the RESTAPI connection timeout with
ZFS Storage Appliance, allow tempest to pass with slower network links.

DocImpact: New config parameter is added to allow configuring timeout value.
Closes-Bug: #1369136

Change-Id: I8de19f56a18106324ed414cf41ee2323de639359
Merge "Timeout triggers failures running tempest for ZFSSA driver."