gdb/reverse: force direction to forward when stopping record

gdb/reverse: force direction to forward when stopping record

If a user had set the execution direction to reverse, and then they use
the command "record stop", the execution direction will be cached as
reversed, which will affect some warning messages, and can confuse
users.

This commit fixes this by forcing the execution direction to "forward"
when the command "record stop" is executed.

Approved-By: Guinevere Larsen <guinevere@redhat.com>