Remove heavy operation in the context of OSGi framework
The routine modeChangeNotify can be called in the context of the OSGi
framework via the chain:
<snip>
at org.opendaylight.controller.forwardingrulesmanager.internal.ForwardingRulesManager.modeChangeNotify(ForwardingRulesManager.java:2137)
at org.opendaylight.controller.switchmanager.internal.SwitchManager.switchManagerAwareNotify(SwitchManager.java:1797)
at org.opendaylight.controller.switchmanager.internal.SwitchManager.setSwitchManagerAware(SwitchManager.java:1677)
</snip>
now given the modeChangeNotify trigger an interaction with the network
element, it's better to keep that off a different thread to avoid to
stuck the OSGi framework for to long.
Change-Id: I41ba96372816cd0a5b2b488bbfc64d10ba2adb4a
Signed-off-by: Giovanni Meo <gmeo@cisco.com>