Allow `adb sync /data` as well as `adb sync data`.

I've been stubbing my toe against this for a decade now... The partition
names may well be "data" or "system", but other commands like push or
pull (or shell) use paths rather than names, so sync is the one weird
exception where you MUST omit the leading slash.

Change-Id: Idcbc94240b7850752966366b6d7889bfdb2e7233
2 files changed