Improve ssh connection debug messages
Improve ssh connection debug messages

1) Mention the host and port in the "Connecting..." message.

2) Mention the username in the post-connection handshaking message.

3) If handshaking fails, mention the user, host, and port in the error
   message that will eventually be returned to the user.

apparentlymart/terraform,brandontosch/terraform,pradeepbhadani/terraform,nlamirault/terraform,pdecat/terraform,heimweh/terraform,pryorda/terraform,rnaveiras/terraform,pdecat/terraform,VladRassokhin/terraform,heimweh/terraform,gechr/terraform,gechr/terraform,nlamirault/terraform,apparentlymart/terraform,ewbankkit/terraform,heimweh/terraform,VladRassokhin/terraform,rnaveiras/terraform,hashicorp/terraform,pdecat/terraform,heimweh/terraform,VladRassokhin/terraform,tommynsong/terraform,pradeepbhadani/terraform,nlamirault/terraform,brandontosch/terraform,pryorda/terraform,hashicorp/terraform,heimweh/terraform,apparentlymart/terraform,VladRassokhin/terraform,tommynsong/terraform,brandontosch/terraform,apparentlymart/terraform,pryorda/terraform,gechr/terraform,brandontosch/terraform,rnaveiras/terraform,ewbankkit/terraform,tommynsong/terraform,pdecat/terraform,ewbankkit/terraform,hashicorp/terraform,ewbankkit/terraform,brandontosch/terraform,apparentlymart/terraform,pradeepbhadani/terraform