When the Hive Metastore creates a subdirectory in the Hive warehouse for
a new table it does so with the default HDFS permissions. Since the default
dfs.umask value is 022, this means that the new subdirectory will not inherit the
group write permissions of the hive warehouse directory.
We should make the umask used by Warehouse.mkdirs() configurable, and set
it to use a default value of 002.