webadmin: set the engine session ID as the reports token

Recent changes in the engine set the session ID differently.
In the past it was identical to the JSESSIONID, but now it is a
generated one.
This patch sets the reports SSO token to the returned session ID upon
login, which is the engine-generated session ID.

Change-Id: Id57589fb6266ca513607f474070bd9769e31c2e5
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1122582
Signed-off-by: Oved Ourfali <oourfali@redhat.com>