factory tests: force mounting partitions with ext2 before running postinst (in R11 factory)

BUG=chrome-os-partner:3940
TEST=none, factory will verify

Change-Id: I2ff22444c9c96d886904aa6359f93a6a1f8301ba
Reviewed-on: http://gerrit.chromium.org/gerrit/5621
Reviewed-by: Jay Kim <yongjaek@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
2 files changed