Bug 5504: Fix IllegalStateException handling from commit
https://git.opendaylight.org/gerrit/#/c/36172 attempted to
handle/workaround IllegalStateException thrown from commit to re-apply
the transaction. However the change wasn't correct - the commit call
actually throws an ExecutionException which the IllegalStateException as
the cause. So we need to catch ExecutionException and check it the cause
is IllegalStateException.
Change-Id: I65b2d646a60a700d070dea822d20b0e649290643
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>