apmanager: claim interfaces when shill appears

In the case of shill starts or restarts after apmanager had claim
interfaces, apmanager needs to claim those interfaces from the
new shill instance.

BUG=chromium:435704
TEST=USE="asan clang" emerge-$BOARD apmanager
Manual Test:
1. Start an AP service on a Marvell based device (glimmer with Marvell chip)
2. Verify mlan0 is not own by shill anymore by executing
   "./usr/local/lib/flimflam/list-devices
3. Restart shill with "restart shill"
4. And verify mlan0 is still no own by shill
5. Termintate the AP service, and verify mlan0 is own by shill

Change-Id: I12f9fde8de6d527c95901e334337fcd97a634993
Reviewed-on: https://chromium-review.googlesource.com/234459
Trybot-Ready: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
2 files changed