Added SElinux as optional parameter.

[frjaraur]

I had a problem working on a SElinux enabled environment and I added a quick patch, adding an option and standard SELinux labels allowing containers to manage CIFS volume content (I wasn´t able to read or write any CIFS volume because SELinux does not allow this operations from containers using its default cifs_t label). If selinuxEnabled: "true" option is used, context=system_u:object_r:container_file_t:s0 will be added as option during mount operation.