ktest: Add CONNECT_TIMEOUT to change the connection timeout time

Before ktest issues a reboot, it will try to connect to the target machine
to make sure that it is still alive. If the target does not respond within 5
seconds, it will power cycle the box instead of issuing a reboot.

Five seconds may be too short, and ktest may unnecessarially power cycle the
box. I have found 25 seconds seems to be a better timeout for this purpose.
But even 25 may be too arbitrary. Add a CONNECT_TIMEOUT option to let the
user determine the timeout time before rebooting. By default, it has been
raised to 25 seconds.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/testing/ktest/sample.conf

@@ -725,6 +725,13 @@
 # (default 120)
 #TIMEOUT = 120
 
+# The timeout in seconds when to test if the box can be rebooted
+# or not. Before issuing the reboot command, a ssh connection
+# is attempted to see if the target machine is still active.
+# If the target does not connect within this timeout, a power cycle
+# is issued instead of a reboot.
+# CONNECT_TIMEOUT = 25
+
 # In between tests, a reboot of the box may occur, and this
 # is the time to wait for the console after it stops producing
 # output. Some machines may not produce a large lag on reboot