Fib::removeNextHopFromAllEntries automatically deletes fib::Entry
if the last nexthop record is being removed.
refs #1341
Change-Id: I36d42fe8f9fc8f03d194f845020aff408cd70488
All tests must use BaseFixture or a fixture derived from it to get this feature.
This commit also fixes a few warnings in tests/mgmt, and moves test cases into nfd::tests namespace.
refs #1290
Change-Id: I891441a5abce170e35648d463f7157b18429f79f