libdm: Fallback to legacy ueventd logic if running on an older system.

When delivering single-stage, non-AB OTAs, the updater binary is built
on a newer OS than recovery is compiled with. libdm relies on newer ueventd
behavior which therefore breaks this model. As a workaround, we allow
libdm to fallback to the old ueventd logic if the following conditions
hold true: (1) we're in recovery, (2) the device is not an AB device,
and (3) the release is <= 10.

Since the old ueventd behavior can lead to races in libdm, this fallback
should stay as narrow as possible.

Bug: 156536673
Bug: 155202260
Test: manual test
Change-Id: I7f9da49e4ba8dfe165e0923d9918827d51d090cd
1 file changed