[3360] Initialize universe when using Memfile backend.

src/bin/dhcp4/dhcp4_srv.h

@@ -88,7 +88,7 @@ public:
     /// @param direct_response_desired specifies if it is desired to
     /// use direct V4 traffic.
     Dhcpv4Srv(uint16_t port = DHCP4_SERVER_PORT,
-              const char* dbconfig = "type=memfile",
+              const char* dbconfig = "type=memfile universe=4",
               const bool use_bcast = true,
               const bool direct_response_desired = true);
 

src/bin/dhcp6/tests/dhcp6_test_utils.h

@@ -45,7 +45,7 @@ class NakedDhcpv6Srv: public isc::dhcp::Dhcpv6Srv {
 public:
     NakedDhcpv6Srv(uint16_t port) : isc::dhcp::Dhcpv6Srv(port) {
         // Open the "memfile" database for leases
-        std::string memfile = "type=memfile";
+        std::string memfile = "type=memfile universe=6";
         isc::dhcp::LeaseMgrFactory::create(memfile);
     }