fix: set connection timeouts + clean up bad contexts

Closes coop-cloud/organising#205.

cli/server/add.go

@@ -118,6 +118,10 @@ All communication between Abra and the server will use this SSH connection.
 		ctx := context.Background()
 		cl, err := client.New(domainName)
 		if err != nil {
+			logrus.Warn("cleaning up context due to connection failure")
+			if err := client.DeleteContext(domainName); err != nil {
+				logrus.Fatal(err)
+			}
 			logrus.Fatal(err)
 		}
 
@@ -125,6 +129,10 @@ All communication between Abra and the server will use this SSH connection.
 			if strings.Contains(err.Error(), "command not found") {
 				logrus.Fatalf("docker is not installed on '%s'?", domainName)
 			} else {
+				logrus.Warn("cleaning up context due to connection failure")
+				if err := client.DeleteContext(domainName); err != nil {
+					logrus.Fatal(err)
+				}
 				logrus.Fatalf("unable to make a connection to '%s'?", domainName)
 			}
 			logrus.Debug(err)