ipahost: Make return value depending on hosts parameter

The way how randompasswords are returned by the ipahost module depends
so far on the number of hosts that are handled by the module.

This is unexpected if for example a json file is provided with the hosts
parameter. As it might be unknown how many hosts are in the json file,
this behaviour is unexpected. The return should not vary in this case.

This chamge makes the return simply depend on the use of the hosts
paramater. As soon as this parameter is used, the return will always be:

"host": { "<the host>": { "randompassword": "<the host random password>" } }

In the simply case with one host it will be still

"host": { "randompassword": "<the host random password>" }

This change for ipahost is related to the ipauser PR #1053.