Stop donating the terminal for bind functions

Unfortunately this causes input coming in while bind functions are
running to show up on screen.

Since the cure is worse than the disease let's just stop doing it.

My guess is this needs to *only* be done while running an external
command.

Fixes #7770
Reintroduces #2114

Partially reverts 5f16a299a7

tests/pexpects/fg.py

@@ -92,11 +92,13 @@ send("\x12")  # ctrl-r, placing fth in foreground
 expect_str("SIGCONT")
 
 # Do it again.
-send("\x1A")
-expect_str("SIGTSTP")
-sleep(0.1)
-send("\x12")
-expect_str("SIGCONT")
+# FIXME: Unfortunately the fix for #2114 had to be reverted because of #7770,
+# so this is broken.
+# send("\x1A")
+# expect_str("SIGTSTP")
+# sleep(0.1)
+# send("\x12")
+# expect_str("SIGCONT")
 
 # End fth by sending it anything.
 send("\x12")