Introduce some default log verbosity control

Move a lot of common error logging into better buckets:

glog.Errorf() - Always an error
glog.Warningf() - Something unexpected, but probably not an error
glog.V(0) - Generally useful for this to ALWAYS be visible
            to an operator
            * Programmer errors
            * Logging extra info about a panic
            * CLI argument handling
glog.V(1) - A reasonable default log level if you don't want
            verbosity
            * Information about config (listening on X, watching Y)
            * Errors that repeat frequently that relate to conditions
              that can be corrected (pod detected as unhealthy)
glog.V(2) - Useful steady state information about the service
            * Logging HTTP requests and their exit code
            * System state changing (killing pod)
            * Controller state change events (starting pods)
            * Scheduler log messages
glog.V(3) - Extended information about changes
            * More info about system state changes
glog.V(4) - Debug level verbosity (for now)
            * Logging in particularly thorny parts of code where
              you may want to come back later and check it

pkg/cloudprovider/plugins.go

@@ -42,7 +42,7 @@ func RegisterCloudProvider(name string, cloud Factory) {
 	if found {
 		glog.Fatalf("Cloud provider %q was registered twice", name)
 	}
-	glog.Infof("Registered cloud provider %q", name)
+	glog.V(1).Infof("Registered cloud provider %q", name)
 	providers[name] = cloud
 }