fix(backend): ensure that we always use default timeout for am requests

Timeout attribute for each alertmanager upstream should default to the value of alertmanager.timeout flag.
Without that it will default to 0s which will cause it to timeout instantly

internal/config/config.go

@@ -172,6 +172,11 @@ func (config *configSchema) Read() {
 	if err != nil {
 		log.Fatal(err)
 	}
+	for i, s := range config.Alertmanager.Servers {
+		if s.Timeout.Seconds() == 0 {
+			config.Alertmanager.Servers[i].Timeout = v.GetDuration("alertmanager.timeout")
+		}
+	}
 
 	err = v.UnmarshalKey("jira", &config.JIRA)
 	if err != nil {