Description of problem:
"ipa radiusproxy-add" command needs to prompt to enter secret key

Version-Release number of selected component (if applicable):
ipa-server-4.4.0-1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
# ipa radiusproxy-add
RADIUS proxy server name: testproxy01
Server: 127.0.0.1
ipa: ERROR: 'ipatokenradiussecret' is required

Actual results:
ipa: ERROR: 'ipatokenradiussecret' is required

Expected results:
It should prompt to enter Secret

Example:
RADIUS proxy server name: testproxy01
Server: 127.0.0.1
Secret: 
Enter Secret again to verify:

Additional info:
There is no way to enter "Secret" in CLI

# ipa radiusproxy-add --help
Usage: ipa [global-options] radiusproxy-add NAME [options]
 
Add a new RADIUS proxy server.
Options:
  -h, --help      show this help message and exit
  --desc=STR      A description of this RADIUS proxy server
  --server=STR    The hostname or IP (with or without port)
  --timeout=INT   The total timeout across all retries (in seconds)
  --retries=INT   The number of times to retry authentication
  --userattr=STR  The username attribute on the user object
  --setattr=STR   Set an attribute to a name/value pair. Format is attr=value.
                  For multi-valued attributes, the command replaces the values
                  already present.
  --addattr=STR   Add an attribute/value pair. Format is attr=value. The
                  attribute must be part of the schema.
  --all           Retrieve and print all attributes from the server. Affects
                  command output.
  --raw           Print entries as stored on the server. Only affects output
                  format.