Simplify NetworkOverlaps function

- Doing a lot of unnecessary things.

Signed-off-by: Alessandro Boch <aboch@docker.com>

libnetwork/netutils/utils.go

@@ -59,17 +59,7 @@ func CheckRouteOverlaps(toCheck *net.IPNet) error {
 
 // NetworkOverlaps detects overlap between one IPNet and another
 func NetworkOverlaps(netX *net.IPNet, netY *net.IPNet) bool {
-	// Check if both netX and netY are ipv4 or ipv6
-	if (netX.IP.To4() != nil && netY.IP.To4() != nil) ||
-		(netX.IP.To4() == nil && netY.IP.To4() == nil) {
-		if firstIP, _ := NetworkRange(netX); netY.Contains(firstIP) {
-			return true
-		}
-		if firstIP, _ := NetworkRange(netY); netX.Contains(firstIP) {
-			return true
-		}
-	}
-	return false
+	return netX.Contains(netY.IP) || netY.Contains(netX.IP)
 }
 
 // NetworkRange calculates the first and last IP addresses in an IPNet