Glob/Wildcard support for roles

[nathkn]

Solves #47

Allows for roles to specify their namespaces as globbed patterns:

vault write auth/kubernetes/role/my-role \
    bound_service_account_names=my-globbed-sa-* \
    bound_service_account_namespaces=my-globbed-namespace-* \
    policies=default \
    ttl=1h

Two main changes:

1. Use StrListContainsGlob instead of StrListContains to allow for
   globbed names/namespaces - seemed like the path of least resistance

2. Update the setupBackend test function to accept the test role's allowed SA
   name/namespace as parameters, allowing testing of globbed namespaces

Not sure if more logic around this is needed since kubernetes names are pretty limited with regard to special characters anyway.

[mterron]

Can someone please take a look at this PR? It'll make k8s auth much more usable for certain use cases.

[jefferai]

Thanks!

[idcmp]

Hey just catching up on this to track issue #47.

Ordering of StrListContainsGlob is undefined, so an entry for "foo" and "f*" may get the "f*" match, or may get the "foo" wildcard. This makes it impossible to have hardcoded service accounts wild a wildcard catch-all (which is likely the most desirable usage of wildcards).