Scale tests: Use exec commands and VAT executor

This is the same appoach as in ipsec tests.
This is the fastest way to fix scale tests.

- Some argument combinations are not supported, e.g. multipath=False.
 + Make multipath=True default.
 - Devicetest using local=True only works with PAPI.
  + But that was true already in rls2106, so no need to fix here.
+ Add two more formats to NetworkIncrement.
+ Check address is aligned, unless call side disables that.
 + Only one keyword for two devicetests disables the check.
+ Papi history condition to print first and last.
+ Minor docstring edits.

Change-Id: I32d24e2f821b412b5841a50d2f87e1c86345b1aa
Signed-off-by: Vratko Polak <vrpolak@cisco.com>