Unlike `docker run -v..`, `docker service create --mount`
does not allow bind-mounting non-existing host paths.
This adds validation for the specified `source`, and
produces an error if the path is not found on the
host.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 84d5ab96ef33355e65f5c31210eb1777db372c52
Component: engine