NEO/py sometimes sends 'None' for boolean values (being equal to 'False'
due to pythons 'bool(None) == False' logic). Let's accept python based
False values (= Nil) as equally acceptable.

Without this patch we can see errors as:

xtesting.go:330: load 0285cbad6e147b66:0000000000000005: returned err unexpected:
        have: neo://127.0.0.1:30002/1: load 0285cbad6e147b66:0000000000000005: 127.0.0.1:48928 - 127.0.0.1:33051 .251: decode: decode: M: AnswerObject.Compression/op: got opcode 00;  expected any from c3c2