Add the following text explaining the risk of using regular
expressions in path lists:
Each member of the list can be a regular expression, but prefer names.
Otherwise, please read and understand the following carefully.
SECURITY WARNING: If you use regular expressions, be mindful that
an attacker could craft an annotation that uses .. to escape the paths
you gave. For example, if your regexp is /bin/qemu.* then if there is
a directory named /bin/qemu.d/, then an attacker can pass an annotation
containing /bin/qemu.d/../put-any-binary-name-here and attack your host.
Fixes: #901
Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>