Fix Checkstyle violations related to exception handling in elanmanager.

Fix Checkstyle violations related to exception handling in elanmanager.

read
https://wiki.opendaylight.org/view/BestPractices/Coding_Guidelines#IllegalCatch

This change also includes a few additional non-Exception handling
related minor Checkstyle fixes, and can now enable enforcement of
Checkstyle for elanmanager.  (This is not directly related to the
exception handling fixes, but those were simply the last Checkstyle
violations left, and in order to ensure future non-regression, we can
now, finally, enable enforcement.)

Change-Id: If233f3d856b2f5402ef551f8ceceb242376b671c
Signed-off-by: Michael Vorburger <vorburger@redhat.com>
Signed-off-by: Sam Hague <shague@redhat.com>