AppArmor is very strict when it comes to specifying the target of a
mount rule: when the mount refers to a directory, the target *must* end
with a "/", or AppArmor will block the operation. We did not catch this
in our tests because we have always been ending our "where" attributes
with a "**", that also matches slashes.
So, we update the rule to allow for an optional "/" at the end of the
mount target specification; note that our regular expression for the
validation of the mount target attribute is written in such a way that
an ending slash is not allowed. For the time being this seems proper,
because we don't want to expose this subtlety to the developer.
a10ecaaaaf