[POLICY-75] Problems with KieScanner

[POLICY-75] Problems with KieScanner

1) Change the 'PolicySession.DefaultThreadModel' thread so it
   continually calls 'fireUntilHalt' until it is explicitly stopped by
   the 'stop()' method. This allows it to restart after 'KieScanner'
   triggers an update.

2) Remove call to 'startScanner' in 'PolicyContainer' constructor --
   we saw at least one case where 'KieScanner' would repeatedly update
   the Drools container every 60 seconds.

Change-Id: I0d0e6c5650cef12ca00cf88f9b8cc52323bb6317
Signed-off-by: Ralph Straubs <rs8887@att.com>