Fix terminal mess-up after killing console or editor

After killing a console or an editor called by virsh *edit command,
The terminal will possibly messed up or the scrolling will be
disabled.

This patch reset the terminal by calling 'stty sane' and 'tput rmcup'
after every virsh command call.

Also this patch ensures killing the process even if killed by keyboard
interrupt.

Signed-off-by: Hao Liu <hliu@redhat.com>