Description of problem:
In RHUI v2, we can upload RHUI content cert with using 'cert upload' sub command of rhui-manager however it seems disappeared in RHUI v3.


Version-Release number of selected component (if applicable):
3.0 Beta.1


How reproducible: Always


Additional info:
If it's difficult or takes some to implement this into rhui-manager.
An wrapper script or something does this may be enough such like:

----------------------------------------------------
#! /bin/bash
# installed as /usr/sbin/rhui-manager_cert_upload.sh or something.
set -e

usage="$0 CERT_PATH"
if test $# -lt 1; then
    echo $usage
    exit 1
fi

read -s -p 'Password: ' -t 5 passwd
cat << EOC | rhui-manager --username admin --password ${passwd:?}
n
u
${1}
y
q
EOC
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