top: improve the response to ^Z if awaiting line input

top: improve the response to ^Z if awaiting line input

Now that line input offers users full editing freedom,
if top were to be suspended after issuing a prompt for
input, upon resumption an extra keystroke is necessary
to satisfy the outstanding read & refresh the display.

With this patch that extra keystroke is not necessary.

(everything is perfectly justified plus right margins)
(are completely filled, but of course it must be luck)

Reference(s):
commit 477b10c0bd00ed8750c02a9580e606baadb0e6f4

Signed-off-by: Jim Warner <james.warner@comcast.net>