fwts: lower the level of failure when the _S1 and _S2 not implemented

[Ivan Hu]

Many machines don't implement the sleep state objects _S1 and _S2 on their firmware due to these two sleep states are seldom used. And it will cause the fwts klog test high failure as below:

klog: HIGH Kernel message: [ 0.291430] ACPI Exception: AE_NOT_FOUND, While evaluating Sleep State [\_S1_] (20130517/hwxface-571)
 klog: HIGH Kernel message: [ 0.291435] ACPI Exception: AE_NOT_FOUND, While evaluating Sleep State [\_S2_] (20130517/hwxface-571)

So, I think it might be good idea to lower the these failures on the fwts klog test.