Refactor disk mounting logic to set full permissions on disks.

[brdeyo]

• Set full permissions on the root directory for each mount point (e.g. chmod 777, chown).
• Update PostgreSQL database configuration and distribution logic to use a "subdirectory" within the mount point directory. PostgreSQL requires the "postgresql" user to have ownership of the directory in which database/tablespace files exist. We DO NOT want these permissions applied to the root mount point directory as it would impact all other workloads trying to access the file system through the mount point.
• Update MySQL database configuration and distribution logic to use a "subdirectory" within the mount point directory. Same reason as for PostgreSQL for the "mysql" user ownership dilemma.