refactor 4+6 to use alt image with ipv6 support

Change-Id: I1134568473abca0c47e88766450d74c81dd63981
Megre upstream 19.09.14
refactor 4+6 to use alt image with ipv6 support after review

Change-Id: I14eab909445446ed36e1109d20f4ee669b8502ac
Fix ping command if no IP version is specified
remove basic ipv6 tests inherited from basic ipv4, since won't work due to attempt to assign  floating ipv4 to private ipv6

Change-Id: I91fa47e4fe3cadd41f5f989bb172960ae0dbfbdb
Merge pull request #32 from kshileev/test

refactor 4+6 to use alt image with ipv6 support
Merge pull request #33 from kshileev/remove-basic-ipv6

remove basic ipv6 tests inherited from basic ipv4, since won't work due ...
Additional IPv6 tests

Add router interfaces
Add port delete check