go.crypto: remove unreachable code.

I ran go vet over all of go.crypto and removed lots of panic("unreachable") that are no longer needed.

R=golang-dev, r, dgryski
CC=golang-dev
https://golang.org/cl/10113043

ssh/channel.go

@@ -340,8 +340,6 @@ func (c *serverChan) read(data []byte) (n int, err error, windowAdjustment uint3
 
 		c.cond.Wait()
 	}
-
-	panic("unreachable")
 }
 
 // getWindowSpace takes, at most, max bytes of space from the peer's window. It

ssh/client_auth.go

@@ -286,7 +286,6 @@ func (p *publickeyAuth) confirmKeyAck(key interface{}, t *transport) (bool, erro
 			return false, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
 		}
 	}
-	panic("unreachable")
 }
 
 func (p *publickeyAuth) method() string {
@@ -325,7 +324,6 @@ func handleAuthResponse(t *transport) (bool, []string, error) {
 			return false, nil, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
 		}
 	}
-	panic("unreachable")
 }
 
 // ClientAuthKeyring returns a ClientAuth using public key authentication via

ssh/server.go

@@ -730,8 +730,6 @@ func (s *ServerConn) Accept() (Channel, error) {
 			}
 		}
 	}
-
-	panic("unreachable")
 }
 
 // A Listener implements a network listener (net.Listener) for SSH connections.

ssh/server_terminal.go

@@ -77,5 +77,4 @@ func (ss *ServerTerminal) ReadLine() (line string, err error) {
 			ss.Channel.AckRequest(ok)
 		}
 	}
-	panic("unreachable")
 }

ssh/session_test.go

@@ -62,7 +62,6 @@ func dial(handler serverType, t *testing.T) *ClientConn {
 				handler(ch.(*serverChan), t)
 			}()
 		}
-		<-done
 	}()
 
 	config := &ClientConfig{

ssh/transport.go

@@ -139,7 +139,6 @@ func (t *transport) readPacket() ([]byte, error) {
 			return packet, nil
 		}
 	}
-	panic("unreachable")
 }
 
 // Encrypt and send a packet of data to the remote peer.