Bug 2192 - Part2 - Move getProperty() to a common util module

With this change, the calls to obtain non-default configurations for OVSDB
have been moved to a single function.

This is the merge of https://git.opendaylight.org/gerrit/#/c/12176/ from master to stable/helium

Conflicts:
	README
	commons/parent/pom.xml
	openstack/net-virt-providers/pom.xml
	ovs-sfc/pom.xml

Change-Id: I0794d1f95d9388d056b5d2fbe8e0e9b5addb7859
Signed-off-by: Flavio Fernandes <ffernand@redhat.com>