Check for system_other existence in recovery mode as well. am: 13e4195d65 am: 226f3bf394 am: d77a11c89f am: 320de84429 am: 4145c66c85

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1325774

Change-Id: Iba25eb120e044ba4f76ec764a7f78ccb2274473b