Support for manual method + rearrange some code

Ticket: CM-1438
Reviewed By:
Testing Done:

- Moved link config to base ifupdown. I had been debating about this,
  this is need to support manual and also the --no-scripts option.
- helps executing only link up/down operations if needed on an interface
- While at it, i also moved the scheduler methods to be classmethods
  instead of instance methods (which again was a pending cleanup task)

sbin/ifupdown

@@ -275,7 +275,6 @@ handlers = {'up' : run_up,
 def main(argv):
     """ main function """
     args = None
-
     try:
         op = None
         if re.search(r'ifup', argv[0]) != None: