webadmin: Added sorting of hosts by SPM priority upon activating

When sending a multiple activate host command the list of the hosts is not
oredered by SPM priority and that can cause a scenario in which no SPM is
elected, multiple hosts are activated one after another and the first one
is selected as an SPM regardless of the SPM priority of the rest.
In order to avoid this scenario, the list is sorted by SPM priority prior
to running the multiple actions

Change-Id: Ie1b3f564491372c8934451c774127ae29e1ac879
Bug-Url: https://bugzilla.redhat.com/998997
Signed-off-by: Tal Nisan <tnisan@redhat.com>