bug#52115: Suggestion: LN command should swap TARGET and LINK_NAME if LINK_NAME already exists

[Warren Parad]

It is too frequent a problem to know which is the correct order of TARGET
and LINK_NAME.

Since the command already believes that it can't create a link to a file
which already exists (and for hard links that the TARGET must also exist),
instead of complaining, the command should just switch the order of the
parameters.