Print host before output in multihost mode (#630)

cyber-dojo uses the multi-host trick and recently we had a CI run where different bits of output were originating from different hosts. It was not at all clear to read. This PR prefixes the main output (from the main host - zeroth host) with the host. For example, instead of "OK" you now get "[https://app.kosli.com]\nOK"

Author: JonJagger

cmd/kosli/multiHost.go

@@ -5,13 +5,14 @@ Kosli uses CI pipelines in the cyber-dojo Org repos [*] for two purposes:
 1. public facing documentation
 2. private development purposes
 
-All Kosli CLI calls in [*] are made to _two_ servers (because of 2)
+All Kosli CLI calls in [*] are made to _three_ servers (because of 2)
   - https://app.kosli.com
   - https://staging.app.kosli.com
+  - https://app.us.kosli.com
 
-Explicitly making each Kosli CLI call in [*] twice is not an option (because of 1)
-Duplicating the entire CI workflows is complex because, eg, deployments must not be duplicated.
-The least-worst option is to allow KOSLI_HOST and KOSLI_API_TOKEN to specify two
+Explicitly making each Kosli CLI call in [*] three times is not an option (because of 1)
+Duplicating the entire CI workflows is complex, eg, deployments must not be duplicated.
+The least-worst option is to allow KOSLI_HOST and KOSLI_API_TOKEN to specify multiple
 comma-separated values. Note cyber-dojo must ensure its api-tokens do not contain commas.
 */
 
@@ -52,7 +53,7 @@ func runMultiHost(args []string) (string, error) {
 	args0 := argsAppendHostApiTokenFlags(0)
 	output0, err0 := runBufferedInnerMain(args0)
 
-	stdOut := output0
+	stdOut := fmt.Sprintf("[%s]\n", opts.hosts[0]) + output0
 	var errorMessage string
 
 	if err0 != nil {

cmd/kosli/multiHost_test.go

@@ -118,7 +118,7 @@ func (suite *MultiHostTestSuite) TestRunDoubledHost() {
 		{
 			name:   "only returns primary call output when both (2) calls succeed",
 			args:   doubledArgs([]string{"kosli", "status"}),
-			stdOut: []string{"OK", ""},
+			stdOut: []string{"[http://localhost:8001]", "OK", ""},
 			err:    error(nil),
 		},
 	} {
@@ -153,7 +153,7 @@ func (suite *MultiHostTestSuite) TestRunTripledHost() {
 		{
 			name:   "only returns primary call output when all three calls succeed",
 			args:   tripledArgs([]string{"kosli", "status"}),
-			stdOut: []string{"OK", ""},
+			stdOut: []string{"[http://localhost:8001]", "OK", ""},
 			err:    error(nil),
 		},
 	} {