Before this patch, Gophercloud attempted to create a security group rule
that would be applied regardless of the protocol by passing the literal
`"any"` as the rule protocol.

Despite being correct according to [the documentation][1], Neutron
rejects the value `"any"` with an HTTP status code of  `400 Bad
Request`.

This change replaces the value of `ProtocolAny` to be the empty string
`""`, which has the effect of creating a rule that applies to any
protocol.

cf: [Neutron bug 2074056][2]

[1]: https://docs.openstack.org/api-ref/network/v2/#create-security-group-rule
[2]: https://bugs.launchpad.net/neutron/+bug/2074056

…otocol

Fix security group rule "any protocol"

Prepare v1.14.1