AbstractServices need unique flowIds in order to avoid rules coalescing

AbstractServices need unique flowIds in order to avoid rules coalescing

This is a follow up from gerrit https://git.opendaylight.org/gerrit/#/c/19410/.
When assembling different flow rules for different match, it is important
to make their flowIds unique. By not doing that, openflowPlugin will treat
them as one; and that is what gets pushed to OF capable node.

Also removed cases when writeFlow() was being invoked twice for no reason.

Change-Id: I898d777e779e61da3c9f070306915c4c37f65572
Signed-off-by: Flavio Fernandes <ffernand@redhat.com>