TetherController - clear both ebpf tether offload maps on startup

This clears out any stale state from a potential previous run.

(also fix a bug... get...MapFd() return -errno on error)

Test: build, atest
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I4a452280a3754ef05964630809efb8cca2bbb833
1 file changed