The PDQ gluster-swift-plugin RPMs default the account, container and object server "mount_check" option to "false" in the sample configuration files. This can be dangerous, and helpful to new users, where if they don't have the gluster volume properly mounted, their Swift REST API based file creations will possibly occur on the root volume if they are not careful. This option should default to "true", and the sample configuration file should advise customers to only turn this off after they are confident their volumes are always mounted ahead of the swift *-server processes.
This is not a bug. For the RHS 2.0 based code, including PDQ, the mount_check option is false to prevent the swift code from doing the mount checking, allowing DiskFile and DiskDir modules to do it. Upstream they are integrated and so this only matters there.