Bug-5559: L2Switch distribution job does not work correctly

Bug-5559: L2Switch distribution job does not work correctly
- replaced hard-coded versions with properties in parent pom
- removed/fixed redundant versions in pom
- when karaf was run from distribution job, it was throwing exceptions. Fixed root-cause which was that karaf.version was set to old version. Now letting this version flow from the parent
- verified using mininet that l2switch features are working as expected when launched from distribution job

Change-Id: Ib2e24fdf1b05e5c42285c3ffe749fca6fbee3617
Signed-off-by: Ajay <ajayl.bro@gmail.com>