RFR(xxs): 8146695: FinalizeTest04 crashes VM with EXCEPTION_INT_DIVIDE_BY_ZERO

[sangheon]

Hi all,

Could I have reviews for the below tiny change to avoid zero division?

Recent change introduced to divide by current non-daemon thread count 
and we need to check the value to be at least larger than zero when we 
divide.

CR: https://bugs.openjdk.java.net/browse/JDK-8146695
Webrev: http://cr.openjdk.java.net/~sangheki/8146695/webrev.00/
Testing: JPRT

Thanks,
Sangheon