wiggle: return the wiggled result from set-wiggle.

wiggle: return the wiggled result from set-wiggle.

If set-wiggle is given ->comm2, and if there are no conflicts, return
the successful wiggle as a string.
Also if the attribute passed is an empty string, don't add any markup.
This can be used to only get the wiggle.

The intention of the "wiggle" command was to return the wiggle, but
there is some much commonality with set-wiggle that it seemed easiest to
add the functionality there.
So discard the unimplemented 'wiggle' command.

Signed-off-by: NeilBrown <neil@brown.name>