Provide a Http Schedule Method

Right now we have INKContSchedule , it provides the plugin to schedule tasks related to a continuation but
INKHttpTxnReenable would fail if it is called after that as it the HttpSM lock is not held when the HttpSM main handler
is called. A neat way of doing this would be providing an interface to schedule Http related activities
INKHttpContSchedule which activates the HttpSM continuation and SM calls the Continuation handler

• copied from bugzilla 3211215
  need to merge the change to open source