__fish_print_hostnames outputs "host" and "hostname"

There's some strange code in `__fish_print_hostnames` that tries to split a line on `=` which, as far as I can tell, isn't supported in `ssh_config(5)`. This has the effect that `__fish_print_hostnames` incorrectly outputs "hostnames" of "host" and "hostname", which means that `fish` thinks these are valid completions for a host.

That is, you get something like:

````sh
$ ssh ho[tab]
Host  (Hostname)  HostName  (Hostname)  Hostname  (Hostname)  
````

This PR fixes this, and also eliminates any wildcarded "hostnames" that might appear in `/etc/ssh/ssh_config` and `~/.ssh/config`.