Also clear DNS state when calling destroy network

Implemented for both binder and CommandListener versions.
If there are not callers of ndc, then we can in a future
change delete CommandListener::ResolverCmd.

Also: require NETWORK_STACK instead of CONNECTIVITY_INTERNAL.

Bug: 34953048
Bug: 64133961
Test: as follows
    - built
    - flashed
    - booted
    - runtest -x system/netd/tests/netd_integration_test.cpp
Change-Id: I232645c5a2f5196523ee42745de3c82349cd9e57
2 files changed