Update help string to match API doc

This changes the text to match what we are stating in
the API documentation (clarifying with review 46569).

Since there is no validation, no changes were made for
peer-address, which is now a string and not IPAddress.
Also, we are leaving peer-id as mandatory, per the API
document.

bug-1225129

Change-Id: I9c3f14213785084349b56a4081e34c209b878ec4
Merge "Update help string to match API doc"