After pruning elements from the VPP configuration, also remove them
from the configuration. The purpose of this is to leave a reasonable
representation of the VPP state in the configuration, so that subsequent
creates and syncs do not have to query the VPP API repeatedly.
The goal of this change is to be able to plan a complete path from
prune, create and sync, with only reading the initial VPP configuration
once, not multiple times.
- Add a get_sub_interfaces() call to fetch all DPDK / Bond sub-ints
- In prune_bvis(), prune_loopbacks() and prune_sub_interfaces(),
use sub_number_of_tags to go out-to-in (qinx, dot1x, untagged)
