[master] Use LeaseMgrFactory::instance() rather than constructor.

This fixes issues reported by the coverity scans recently.

src/bin/dhcp4/tests/ctrl_dhcp4_srv_unittest.cc

@@ -361,7 +361,7 @@ TEST_F(CtrlChannelDhcpv4SrvTest, controlLeasesReclaim) {
                                 time(NULL) - 100, SubnetID(1)));
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease0));
     ASSERT_NO_THROW(lease_mgr.addLease(lease1));
 
@@ -419,7 +419,7 @@ TEST_F(CtrlChannelDhcpv4SrvTest, controlLeasesReclaimRemove) {
                                 time(NULL) - 100, SubnetID(1)));
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease0));
     ASSERT_NO_THROW(lease_mgr.addLease(lease1));
 

src/bin/dhcp4/tests/kea_controller_unittest.cc

@@ -377,7 +377,7 @@ TEST_F(JSONFileBackendTest, timers) {
     lease_reclaimed->state_ = Lease4::STATE_EXPIRED_RECLAIMED;
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease_expired));
     ASSERT_NO_THROW(lease_mgr.addLease(lease_reclaimed));
 

src/bin/dhcp6/tests/ctrl_dhcp6_srv_unittest.cc

@@ -436,7 +436,7 @@ TEST_F(CtrlChannelDhcpv6SrvTest, controlLeasesReclaim) {
     lease1->cltt_ = time(NULL) - 100;
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease0));
     ASSERT_NO_THROW(lease_mgr.addLease(lease1));
 
@@ -498,7 +498,7 @@ TEST_F(CtrlChannelDhcpv6SrvTest, controlLeasesReclaimRemove) {
     lease1->cltt_ = time(NULL) - 100;
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease0));
     ASSERT_NO_THROW(lease_mgr.addLease(lease1));
 

src/bin/dhcp6/tests/kea_controller_unittest.cc

@@ -321,7 +321,7 @@ TEST_F(JSONFileBackendTest, timers) {
     lease_reclaimed->state_ = Lease6::STATE_EXPIRED_RECLAIMED;
 
     // Add leases to the database.
-    LeaseMgr& lease_mgr = LeaseMgrFactory().instance();
+    LeaseMgr& lease_mgr = LeaseMgrFactory::instance();
     ASSERT_NO_THROW(lease_mgr.addLease(lease_expired));
     ASSERT_NO_THROW(lease_mgr.addLease(lease_reclaimed));