adb: Support rescue install and getprop.

Bug: 128415917
Test: Enter rescue mode on taimen. Send the following commands:
      `adb rescue getprop ro.build.fingerprint`
      `adb rescue getprop ro.build.date.utc`
      `adb rescue getprop ro.build.invalid`
      `adb rescue install /path/to/package.zip`
Test: Sideload on taimen w/ `adb sideload /path/to/package.zip`.
Change-Id: Ia246b30314fbcd2bd4cc71a8085a280e33041967