Fixes#3801.
Fixes#3802.
Fixes KEYMAN-WINDOWS-5M.
Fixes KEYMAN-WINDOWS-5N.
This is a two-part fix for Keyman Configuration where it appears there
was a race with creating a temporary file, and which caused a cascading
exception.
The first part resolves the race; the second part (in
UfrmInstallKeyboard.pas) adds a little extra robustness (probably not
totally necessary).