timer_management: Deal with different date format for windows guest. 

Signed-off-by: Yu Mingfei <yumingfei@cn.fujitsu.com>
Yes, i find you add it in https://github.com/yumingfei/tp-libvirt/commit/7410549a89d6968966c0721bb7e7ca89cb7b8c99, but it's still need some work to process the operation as 'stress' is the right recognizable key word in func ```manipulate_vm()```.
BTW, I suggest use 'operation_type' or such kind parameter to instead of 'stress_type'