Case update and bug fix

1. Move test steps into try..finally block, so the env can restore in
any reason fail.
2. When crash guest via session command, it may raise 2 type Exceptions,
so catch them all to pass this step.
3. If the guest started with X window, the old grep keyword can not find
the tty1 process, so just use 'tty1' keyword for the checking.

Signed-off-by: Yanbing Du <ydu@redhat.com>