ktest.pl: Give back console on Ctrt^C on monitor

stable inclusion
from stable-v5.10.173
commit 0dfb3f4588bc03d344e4ca4a70a06f24cf0cf6ec
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8BFR3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0dfb3f4588bc03d344e4ca4a70a06f24cf0cf6ec



--------------------------------

commit 83d29d43 upstream.

When monitoring the console output, the stdout is being redirected to do
so. If Ctrl^C is hit during this mode, the stdout is not back to the
console, the user does not see anything they type (no echo).

Add "end_monitor" to the SIGINT interrupt handler to give back the console
on Ctrl^C.

Cc: stable@vger.kernel.org
Fixes: 9f2cdcbb ("ktest: Give console process a dedicated tty")
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>