This makes the publicrpc service available to the admin CLI
regardless of whether the publicrpc socket is enabled on the node.
Change-Id: If0265f3cd14af44a7f8e9726af796f8879dd7a4b
This allows us to use UNIX filesystem permissions for access control.
Previously, any process in the network namespace could connect to it,
which is insecure for obvious reasons.
Verified that correct permissions are set:
```
# ls -lisa /run/bridge/
total 8
31996269 4 drwxrwxrwx 2 root root 4096 Nov 23 21:58 .
14676759 4 drwxr-xr-x 1 root root 4096 Nov 23 21:58 ..
31996306 0 srwx------ 1 root root 0 Nov 23 21:58 agent.sock
```
Fixes#119