af-packet: fix cppcheck false positive

[src/source-af-packet.c:1903]: (error) Resource leak: fd

src/source-af-packet.c

@@ -1886,7 +1886,9 @@ int AFPIsFanoutSupported(void)
 {
 #ifdef HAVE_PACKET_FANOUT
     int fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
-    if (fd != -1) {
+    if (fd < 0)
+        return 0;
+
     uint16_t mode = PACKET_FANOUT_HASH | PACKET_FANOUT_FLAG_DEFRAG;
     uint16_t id = 1;
     uint32_t option = (mode << 16) | (id & 0xffff);
@@ -1898,9 +1900,9 @@ int AFPIsFanoutSupported(void)
         return 0;
     }
     return 1;
-    }
-#endif
+#else
     return 0;
+#endif
 }
 
 static int AFPCreateSocket(AFPThreadVars *ptv, char *devname, int verbose)