* control: safely restart DHCP server

* control: use mutex in all POST,PUT,DELETE handlers

control.go

@@ -12,6 +12,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/dnsforward"
@@ -36,6 +37,8 @@ var client = &http.Client{
 	Timeout: time.Second * 30,
 }
 
+var controlLock sync.Mutex
+
 // ----------------
 // helper functions
 // ----------------