Bug Fixes and Enhancements

- Bug due to recent callable change: When using more than one executor concurrently
   we need multiple threads in the pool or system deadlocks
- Bug: external-ids in Openstack/OVS Yang needs to be a list
- Enhancement: Changed SFP Yang so that it is a collection of hops that are a combination of SF & SFF
- Bug: Changed SF yang so that it can contain a list of locators instead of single container
- Fixed initial config files accordingly
- Bug: SFP Data Listener needs to listen to scope BASE otherwise we create an inifite loop

Change-Id: I2243e82b530baf549685cbcb7722fcb7f4517e24
Signed-off-by: Reinaldo Penno <rapenno@gmail.com>