fix checking for tls certificates, and the quickstart with the -exist…

…ing-webserver flag

some time ago, the flag to ParseConfig() to do or skip checking the tls
keys/certs was inverted, but it looks like i didn't change the call sites... so
during "mox config test", and after a regular "mox quickstart" there was no
check for the tls keys/certs, and during "mox quickstart -existing-webserver"
there was a check where there shouldn't be. this made using -existing-webserver
impossible.

this became clear with the question by morki in issue #5.

main.go

@@ -512,7 +512,9 @@ are printed.
 		c.Usage()
 	}
 
-	_, errs := mox.ParseConfig(context.Background(), mox.ConfigStaticPath, true, false, false)
+	mox.FilesImmediate = true
+
+	_, errs := mox.ParseConfig(context.Background(), mox.ConfigStaticPath, true, true, false)
 	if len(errs) > 1 {
 		log.Printf("multiple errors:")
 		for _, err := range errs {

quickstart.go

@@ -645,8 +645,8 @@ too many authentication failures).
 	xwritefile("config/domains.conf", []byte(dconfstr), 0660)
 
 	// Verify config.
-	skipCheckTLSKeyCerts := existingWebserver
-	mc, errs := mox.ParseConfig(context.Background(), "config/mox.conf", true, skipCheckTLSKeyCerts, false)
+	loadTLSKeyCerts := !existingWebserver
+	mc, errs := mox.ParseConfig(context.Background(), "config/mox.conf", true, loadTLSKeyCerts, false)
 	if len(errs) > 0 {
 		if len(errs) > 1 {
 			log.Printf("checking generated config, multiple errors:")