Fix typo in zkrb_strings_stat_callback().
Fix typo in zkrb_strings_stat_callback().

Previously assigned to the wrong union member -- not super likely
to cause a problem, but illegal per C99 strict aliasing.

songling88/zookeeper,songling88/zookeeper,zk-ruby/zookeeper,songling88/zookeeper,rickypai/zookeeper,zk-ruby/zookeeper,songling88/zookeeper,rickypai/zookeeper,rickypai/zookeeper,zk-ruby/zookeeper,rickypai/zookeeper