http: Improve auto HTTP->HTTPS redirects, fix edge cases

See https://caddy.community/t/v2-issues-with-multiple-server-blocks-in-caddyfile-style-config/6206/13?u=matt

Also print pid when using `caddy start`

cmd/commands.go

@@ -130,7 +130,7 @@ func cmdStart() (int, error) {
 	// when one of the goroutines unblocks, we're done and can exit
 	select {
 	case <-success:
-		fmt.Println("Successfully started Caddy")
+		fmt.Printf("Successfully started Caddy (pid=%d)\n", cmd.Process.Pid)
 	case err := <-exit:
 		return caddy.ExitCodeFailedStartup,
 			fmt.Errorf("caddy process exited with error: %v", err)