core: executing squartz job immediately

This patch adds an option in the SchedulerUtil API to execute
scheduled job immediately.

SchedulerUtil#triggerJob method, that executes immediately the job with
the given id, was added.

Relevant unit test was added and set to be disabled like the rest of
the similar tests which already exists.

Change-Id: I4661691ae970e7517a4e3a43ae87736ebd1cc15f
Bug-Url: https://bugzilla.redhat.com/888396
Signed-off-by: Arik Hadas <ahadas@redhat.com>
core: start 'prestarted VMs' immediately after update

This patch solves a bug in which after increasing the number of
prestarted VMs of a pool, it takes a while (which is defined by the
configuration value "VmPoolMonitorIntervalInMinutes") to start
more VMs to meet the updated number of prestarted VMs.

The solution is to trigger the pool monitoring job to run immediately,
after UpdateVmPoolWithVmsCommand updates the new properties of the
pool.

Change-Id: I636f496b241c042962cfec10880fbee00ce2bab4
Bug-Url: https://bugzilla.redhat.com/888396
Signed-off-by: Arik Hadas <ahadas@redhat.com>