svirt_start_destroy: Add more test cases

2014-08-26 Update:
Moved the attach pool vol disk cases to new PR 302

svirt_start_destroy: Add test cases with security_driver as none
svirt_start_destroy: Add bug number to label restore FAIL cases
svirt_start_destroy: Update seclabel functions
Update set_seclabel use list in svirt test cases
svirt_start_destroy: Add cases for multiple seclabels
svirt_start_destroy: Add cases for security_default_confined as 0
svirt_start_destroy: Add negative cases for security_require_confined as 1
@waynesun09, `vm.destroy()` actually send a `shutdown` through a session, `vm.destroy(gracefully=False)` might be the expected. I found this could be a legacy issue. Could you please help check and fix this?