node: fix deprecated Iterable import in py3.10

Import from collections.abc instead if import from collections
fails.

Author: shenghaoyang

Diff for: testgres/node.py

@@ -6,7 +6,11 @@
 import subprocess
 import time
 
-from collections import Iterable
+try:
+    from collections import Iterable
+except ImportError:
+    from collections.abc import Iterable
+
 from shutil import rmtree
 from six import raise_from, iteritems, text_type
 from tempfile import mkstemp, mkdtemp