do not unescape sequence in original name in GetRecommendedName()

Noted with the fix for fdo#81304 the code unescaped an escaped sequence
in the original file name, for example "foo%20bar" became "foo bar".
This change preserves such sequences, though the final result at the
(GTK) file picker is still unescaped, which happens somewhere else.

However, now for the suggested file name "foo%20bar#baz" an InetURLObj
of "foo%2520bar%23baz" is created and results in a recommended name of
"foo%20bar#baz" again.

Change-Id: I620811e33bdb74323ddcb3d732428179bf7181d4