Fix dynamic executor appending to objects

Set() has no the append() method.
Unify the _objects to be always assigned a list.
Take the safer remove() approach for the non-unique locks,
if any happened in the image uploader locks manager.

Closes-Bug: #1851502
Change-Id: I1f15441ef31f530758f1588e8006cc6b17d3aeaf
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>
(cherry picked from commit 0b77267d5e)

tripleo_common/image/image_uploader.py

@@ -1146,7 +1146,7 @@ class PythonImageUploader(BaseImageUploader):
         LOG.debug('Starting acquire for lock %s' % layer)
         with lock.get_lock():
             LOG.debug('Acquired for unlock %s' % layer)
-            if layer in lock.objects():
+            while layer in lock.objects():
                 lock.objects().remove(layer)
             LOG.debug('Updated lock info %s' % layer)
         LOG.debug('Released lock on layer %s' % layer)

tripleo_common/utils/locks/threadinglock.py

@@ -19,4 +19,4 @@ from tripleo_common.utils.locks import base
 class ThreadingLock(base.BaseLock):
     def __init__(self):
         self._lock = threading.Lock()
-        self._objects = set()
+        self._objects = []