Check first if event is an RepositoryRegistryEventAdd, to avoid triggering a system status renewal / check if Nexus is started

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Attempt to stabilize the test.

The "window" used by FewSecondsScheduler of 2.4s
was too narrow, and probably made possible to
finish the iteration, while test would wait
for max 11 executions (but due to window 0, 1 or 2
executions were more likely).

Anyway, as the UT is time limited (with the for cycle),
widening the schedule is not a problem, as it will
be detected anyway (will not run forever)
Merge remote-tracking branch 'origin/master' into nexus-5727-session-validation-thread
NEXUS-5727: Applied Stuart's advice

Removed the clumsy setSessionDAO method
from fixed classes that were needed only to
"trigger" the member injection.

Using bind.toConstructor works without this.