volatile-binds: Allow creation of subdirectories

volatile-binds: Allow creation of subdirectories

The mount-copybind script will create the parent directory of the bind
mount if it does not exist. But actually, if this is the case, the
service will not even start because of the ConditionPathIsReadWrite.
This patch adds a "or" condition to allow the service to start also if
the parent directory of the bind mount does not exist.

Signed-off-by: Stéphane Veyret <sveyret@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>