Fixes memory leak in MXOSRVR Zookeeper processing

The code was calling the Zookeeper API zoo_get_children() but the
returned children list was not being freed using free_String_vector().

Change-Id: I73b7ed37c859f5cb01adeb1ba287d19a7369da12
Closes-Bug: 1361371
Merge "Fixes memory leak in MXOSRVR Zookeeper processing"