TEST_NUM_from_record has wrong range [4:7] in unpack, int will need 4 bytes [4:8]

[jaui]

TEST_NUM_from_record

def TEST_NUM_from_record(record, endian):
    '''
    given a PTR, MPR or FTR record, extract the test Number.
    Note: TEST_NUM is for these records always located on offset 4..7

                REC_TYP   REC_SUB   TEST_NUM (V4)
           PTR      15       10       4:8
           MPR      15       15       4:8
           FTR      15       20       4:8

          Also note that endian is important here!
    '''
    REC_TYP, REC_SUB = TS_from_record(record)
    TEST_NUM = -1
    if REC_TYP == 15 and REC_SUB in [10, 15, 20]:
        TEST_NUM = int(struct.unpack("%sI" % endian, record[4:8])[0])
    return TEST_NUM