[adb] Fix crash in mdns service removal.

If std::remove_if is a no-op (no service name match), then
std::vector::erase would crash.

Bug: 160025305

Test: test_adb.py
Test: Manual.
1) Enable wireless debugging on multiple devices
2) Disable wireless debugging on all devices

Change-Id: If58b0dda0bb698fd3fd225d9b6a6726a88ae47e0