Add support for PRL update after OMA-DM activation.

BUG=chrome-os-partner:18300
TEST=1. modem factory-reset
     2. modem get-prl  # Note current PRL version
     3. modem activate
     4. Wait until modem fully activated
     5. modem get-prl  # Verify new version

Change-Id: I52e371b5c8073a2aa212c8102df1741b182d36b5
Reviewed-on: https://gerrit.chromium.org/gerrit/50376
Reviewed-by: Ben Chan <benchan@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
Commit-Queue: Thieu Le <thieule@chromium.org>
2 files changed