Fix tests to skip if no GDB enabled:

test_recovery_target_lsn_backup_victim
test_incr_restore_issue_313
test_restore_issue_313

Author: Oleg Gurev

tests/false_positive_test.py

@@ -214,6 +214,7 @@ def test_recovery_target_lsn_backup_victim(self):
         @y.sokolov: looks like this test should pass.
         So I commented 'expectedFailure'
         """
+        self._check_gdb_flag_or_skip_test()
         backup_dir = os.path.join(self.tmp_path, self.module_name, self.fname, 'backup')
         node = self.make_simple_node(
             base_dir=os.path.join(self.module_name, self.fname, 'node'),

tests/incr_restore_test.py

@@ -2429,7 +2429,7 @@ def test_incr_restore_issue_313(self):
         """
         Check that failed incremental restore can be restarted
         """
-        self._check_gdb_flag_or_skip_test
+        self._check_gdb_flag_or_skip_test()
         node = self.make_simple_node('node',
             set_replication=True,
             initdb_params=['--data-checksums'])

tests/restore_test.py

@@ -3866,7 +3866,7 @@ def test_restore_issue_313(self):
         """
         Check that partially restored PostgreSQL instance cannot be started
         """
-        self._check_gdb_flag_or_skip_test
+        self._check_gdb_flag_or_skip_test()
         node = self.make_simple_node('node',
             set_replication=True,
             initdb_params=['--data-checksums'])