ip_count_list increments even if port creation is not successfull

Description: when address allocation fails, bit is not freed.

Change-Id: Ie5c7ce148784eebe1c4a7e6a0e93189c8705b948
Closes-Bug: #1772156
(cherry picked from commit 3ef5e1c)

src/config/common/zkclient.py

@@ -210,7 +210,15 @@ def alloc(self, value=None):
             idx = self._in_use.index(0)
             self._in_use[idx] = 1
 
-        idx = self._get_zk_index_from_bit(idx)
+        try:
+            idx = self._get_zk_index_from_bit(idx)
+        except ResourceExhaustionError as e:
+            if self._in_use.all():
+                self._in_use.pop(1)
+            else:
+                self._in_use[idx] = 0
+            raise ResourceExhaustionError(str(e))
+
         try:
             # Create a node at path and return its integer value
             id_str = "%(#)010d" % {'#': idx}