policy: Fix not removing timers

policy: Fix not removing timers

If service becomes unavailable, due to e.g. the device being removed,
all the related timers should be removed as well otherwise it may cause
crashes such as the following:

Invalid read of size 8
   at 0x4A6597: btd_device_get_service (device.c:5335)
   by 0x40F49F: policy_connect_ct (policy.c:112)
   by 0x4E7F552: ??? (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x4E7EAEA: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x4E7EE87: ??? (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x4E7F1B1: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x40BACF: main (main.c:631)
 Address 0x73b9ba8 is 360 bytes inside a block of size 592 free'd
   at 0x4C2ACE9: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x4E847FE: g_free (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x49C83F: device_free (device.c:624)
   by 0x4BDB29: remove_interface (object.c:658)
   by 0x4BE701: g_dbus_unregister_interface (object.c:1382)
   by 0x4A49DC: btd_device_unref (device.c:5173)
   by 0x41DC46: avdtp_free (avdtp.c:1138)
   by 0x41EE09: connection_lost (avdtp.c:1164)
   by 0x422EA5: session_cb (avdtp.c:2263)
   by 0x4E7EAEA: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x4E7EE87: ??? (in /usr/lib64/libglib-2.0.so.0.4200.1)
   by 0x4E7F1B1: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.4200.1)