`pcs cluster auth` fails with URI::InvalidURIError when hostname contains an underscore (_)

Issue

• pcs cluster auth command fails when hostname contains an underscore character.

# pcs cluster auth node_b --debug
...
--Debug Output Start--
/usr/share/ruby/uri/generic.rb:214:in `initialize': the scheme https does not accept registry part:node_b:2224 (or bad hostname?) (URI::InvalidURIError)
        from /usr/share/ruby/uri/http.rb:84:in `initialize'
        from /usr/share/ruby/uri/common.rb:214:in `new'
        from /usr/share/ruby/uri/common.rb:214:in `parse'
        from /usr/share/ruby/uri/common.rb:747:in `parse'
        from /usr/lib/pcsd/pcs.rb:411:in `send_request'
        from /usr/lib/pcsd/pcs.rb:1199:in `block (2 levels) in run_auth_requests'
--Debug Output End--