[PBCKP-146] stabilize couple of tests.

Author: funny-falcon

tests/cfs_backup.py

@@ -995,6 +995,11 @@ def test_delete_random_cfm_file_from_tablespace_dir(self):
             "FROM generate_series(0,256) i".format('t1', tblspace_name)
         )
 
+        self.node.safe_psql(
+            "postgres",
+            "CHECKPOINT"
+        )
+
         list_cmf = find_by_extensions(
             [self.get_tblspace_path(self.node, tblspace_name)],
             ['.cfm'])
@@ -1044,6 +1049,11 @@ def test_delete_random_data_file_from_tablespace_dir(self):
             "FROM generate_series(0,256) i".format('t1', tblspace_name)
         )
 
+        self.node.safe_psql(
+            "postgres",
+            "CHECKPOINT"
+        )
+
         list_data_files = find_by_pattern(
             [self.get_tblspace_path(self.node, tblspace_name)],
             '^.*/\d+$')