CSIT-562 HC Test: Persistence suite rework, part1

CSIT-562 HC Test: Persistence suite rework, part1

 - rename keywords that check operational data, to distinguish from keywords
that check configuration data
 - modify existing persistence cases so that they don't affect each other
 - add feature-specific persistence tests for: Interface Management, L2 bridge
 - move Interface Management variables to separate file so they can be reused
 - add new tag HC_PERSIST to execute persistence tests separately
 - update existing Honeycomb tags to comply with CSIT conventions

More feature-specific tests to be added in part2.

Change-Id: I8657da4bb9e9a3d5261c04f5f1999b2572f605ef
Signed-off-by: selias <samelias@cisco.com>