Do not filter capabilities for network users during WP-CLI

We use WP-CLI to install WordPress originally. Because this is in
an mu-plugin, it fires in non multisite mode as well.

As I'm typing this, I'm realizing that we should be doing checks
for is_multisite() everywhere instead.
Merge pull request #147 from washingtonstateuniversity/bug/provisioning

[PR] Do not filter capabilities for network users during WP-CLI