Ticket: 3908: quiet single file overwrite.
If target file exists, MC overwrites that file without confirmation.
The bug was introduced in #3149.
How to reproduce:
1. Create two files: `touch a aa`.
2. Stay on "aa".
3. Make sure that Options/Confirmation.../Overwrite option is checked on.
4. Press Shift-F6
5. Edit the "to:" value to "a" ("a" file exists) and press Enter.
Actual result:
The "a" file is overwritten w/o confirmation.
Expected result:
Since the "a" file exists the confirmation dialog must be shown.
The problem is: confirmation dialog requires context UI which was not
created in case of single file rename operation.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>