ssh: Clearer message when ssh without authentication methods
ssh: Clearer message when ssh without authentication methods

When an SSH server responds to us that there are no
authentication methods available print a clearer message.
This happened when debugging multi-machine interconnection
and sent me on a wild goose chase.

Before:

    server offered unsupported authentication methods: unknown

After:

    server offered no authentication methods

Closes #6425
stefwalter/cockpit,petervo/cockpit,xhad/cockpit,harishanand95/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,cockpituous/cockpit,deryni/cockpit,harishanand95/cockpit,mareklibra/cockpit,petervo/cockpit,harishanand95/cockpit,martinpitt/cockpit,deryni/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,Scribery/cockpit,Scribery/cockpit,xhad/cockpit,petervo/cockpit,harishanand95/cockpit,stefwalter/cockpit,larsu/cockpit,larskarlitski/cockpit,petervo/cockpit,martinpitt/cockpit,larsu/cockpit,SotolitoLabs/cockpit,SotolitoLabs/cockpit,garrett/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,Scribery/cockpit,dperpeet/cockpit,michalskrivanek/cockpit,andreasn/cockpit,Scribery/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,xhad/cockpit,michalskrivanek/cockpit,stefwalter/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,andreasn/cockpit,moraleslazaro/cockpit,larskarlitski/cockpit,martinpitt/cockpit,dperpeet/cockpit,harishanand95/cockpit,mareklibra/cockpit,petervo/cockpit,SotolitoLabs/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,Scribery/cockpit,michalskrivanek/cockpit,andreasn/cockpit,larskarlitski/cockpit,martinpitt/cockpit,andreasn/cockpit,mareklibra/cockpit,larsu/cockpit,mvollmer/cockpit,andreasn/cockpit,garrett/cockpit,larsu/cockpit,stefwalter/cockpit,larsu/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,xhad/cockpit,larskarlitski/cockpit,cockpituous/cockpit,harishanand95/cockpit,michalskrivanek/cockpit,garrett/cockpit,deryni/cockpit,michalskrivanek/cockpit,moraleslazaro/cockpit,deryni/cockpit,mareklibra/cockpit,mvollmer/cockpit,stefwalter/cockpit,andreasn/cockpit,Scribery/cockpit,dperpeet/cockpit,deryni/cockpit,petervo/cockpit,andreasn/cockpit,moraleslazaro/cockpit,larsu/cockpit,cockpituous/cockpit,larskarlitski/cockpit,dperpeet/cockpit,cockpituous/cockpit,dperpeet/cockpit,michalskrivanek/cockpit,xhad/cockpit,michalskrivanek/cockpit,xhad/cockpit,deryni/cockpit,garrett/cockpit,mvollmer/cockpit,stefwalter/cockpit,larskarlitski/cockpit,larskarlitski/cockpit,mvollmer/cockpit,cockpituous/cockpit,dperpeet/cockpit,deryni/cockpit,mareklibra/cockpit,harishanand95/cockpit,Scribery/cockpit,martinpitt/cockpit,petervo/cockpit,garrett/cockpit,SotolitoLabs/cockpit,xhad/cockpit,dperpeet/cockpit,moraleslazaro/cockpit