[3736] Remove redundant assignment cppcheck warning in the d2_udp_unittest.cc

src/lib/dhcpsrv/tests/d2_udp_unittest.cc

@@ -113,8 +113,8 @@ public:
 
         FD_ZERO(&read_fds);
 
-        int select_fd = -1;
         // cppcheck-suppress redundantAssignment
+        int select_fd = -1;
         ASSERT_NO_THROW(select_fd = getSelectFd());
 
         FD_SET(select_fd,  &read_fds);