Merge ~troyanov/maas:agent-logs-remove-ts into maas:master

[Anton Troyanov]

refactor(agent): remove timestamp from logs

MAAS Agent stdout is captured with systemd-cat
Because journal has it's own timestamp, we don't want to add extra

Before:
```
Jan 29 13:35:30 maas maas-agent[161449]: 1:35PM INF Logger is configured with log level "info"
Jan 29 13:35:30 maas maas-agent[161449]: 1:35PM INF Started Worker Namespace=default TaskQueue=qc38cw@agent:main WorkerID=qc38cw@agent:161449
Jan 29 13:35:30 maas maas-agent[161449]: 1:35PM INF Service MAAS Agent started
```

After:
```
Jan 30 15:05:04 maas maas-agent[253279]: INF Logger is configured with log level "info"
Jan 30 15:05:04 maas maas-agent[253279]: INF Started Worker Namespace=default TaskQueue=qc38cw@agent:main WorkerID=qc38cw@agent:253279
Jan 30 15:05:04 maas maas-agent[253279]: INF Service MAAS Agent started
```

[Adam Collard (adam-collard)]

I think the change is good, we should have tests that assert about the behaviour of the logger.

[MAAS Lander (maas-lander)]

UNIT TESTS
-b agent-logs-remove-ts lp:~troyanov/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 608339fa5b05fa3155bcb575b488598e746a64fa

review: Approve

[Adam Collard (adam-collard)]

review: Approve

diff --git a/src/maasagent/cmd/maas-agent/main.go b/src/maasagent/cmd/maas-agent/main.go
index 64d893c..5e01329 100644
--- a/src/maasagent/cmd/maas-agent/main.go
+++ b/src/maasagent/cmd/maas-agent/main.go
@@ -45,7 +45,17 @@ type config struct {
 }
 
 func Run() int {
-	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
+	// Use custom ConsoleWriter without TimestampFieldName, because stdout
+	// is captured with systemd-cat
+	// TODO: write directly to the journal
+	consoleWriter := zerolog.ConsoleWriter{Out: os.Stdout, NoColor: true}
+	consoleWriter.PartsOrder = []string{
+		zerolog.LevelFieldName,
+		zerolog.CallerFieldName,
+		zerolog.MessageFieldName,
+	}
+
+	log.Logger = zerolog.New(consoleWriter).With().Logger()
 
 	cfg, err := getConfig()
 	if err != nil {