core: Reduce number of tasks in queue log messages

When the engine server is loaded, there is a message printed to the log.
This patch increases the threshold of the number of waiting tasks from 0
to 5.

Change-Id: Ieb061ed29750184bcdd39af7d8c3fc7d0dcacabd
Bug-Url: https://bugzilla.redhat.com/1130076
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>
(cherry picked from commit 0c9c012b8704794e27d5a44842fd447cc7a2aa24)