Git: Do not pop stash if a command is in progress

Running interactive rebase and choosing edit for a commit causes
stash pop when the commit is expected to be edited

Change-Id: I37249e8486b609dedba143bd130059444f882303
Reviewed-by: Petar Perisin <petar.perisin@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>