allow admin to setfacl the uploads directory

An admin may wish to set posix ACLs on the uploads directory.
Doing so enables another container or process to access the
uploaded files. For example, to enable apache to read files:

    setfacl -m u:48:r-x /var/ftp/pub/uploads
    setfacl -d -m u:48:r /var/ftp/pub/uploads

When vsftpd chowns an uploaded file, it changes the mask such that
apache has effectively no access...

    -bash-4.1# cd /var/ftp/pub/uploads/

    -bash-4.1# ls -ltr
    total 15948
    -rw-------+ 1 1000 ftp   13434 Nov 20 11:19 foo.dat

    -bash-4.1# getfacl foo.dat
    # file: foo.dat
    # owner: 1000
    # group: ftp
    user::rw-
    user:48:r--                     #effective:---
    group::r-x                      #effective:---
    mask::---
    other::---

Therefore, do not chown. Then the effective permission is granted
according to the ACL...

    -bash-4.1# getfacl foo.dat
    # file: foo.dat
    # owner: 1000
    # group: ftp
    user::rw-
    user:48:r--
    group::r-x                      #effective:r--
    mask::r--
    other::rw-