[master] Initialize rcode_ to avoid cppcheck warning

src/bin/dhcp4/tests/dhcp4_srv_unittest.cc

@@ -193,7 +193,9 @@ public:
     ///
     /// Initializes common objects used in many tests.
     /// Also sets up initial configuration in CfgMgr.
-    Dhcpv4SrvTest() {
+    Dhcpv4SrvTest() :
+        rcode_(0)
+    {
         subnet_ = Subnet4Ptr(new Subnet4(IOAddress("192.0.2.0"), 24, 1000,
                                          2000, 3000));
         pool_ = Pool4Ptr(new Pool4(IOAddress("192.0.2.100"), IOAddress("192.0.2.110")));