AST comparison expression root type check for 'AND' is buggy

[chisholm]

For example,

[(type-a:a=1 OR type-b:b=2) AND (type-a:a=2 OR type-b:b=1)]

is okay, but

[type-a:a=1 AND (type-a:a=2 OR type-b:b=1)]

is not:

>>> stix2.pattern_visitor.create_pattern_object("[type-a:a=1 AND (type-a:a=2 OR type-b:b=1)]", version="2.1")

<start of long stacktrace omitted>

  File "C:\Programming\python\stix\cti-python-stix2\stix2\patterns.py", line 534, in __init__
    super(AndBooleanExpression, self).__init__("AND", operands)
  File "C:\Programming\python\stix\cti-python-stix2\stix2\patterns.py", line 514, in __init__
    raise ValueError("All operands to an 'AND' expression must have the same object type")
ValueError: All operands to an 'AND' expression must have the same object type

The latter pattern simply drops a disjunct from the first 'OR' from the first pattern. If the first is okay, the second should be too. Another example is:

[(type-a:a=1 OR type-a:b=2) AND (type-a:a=2 OR type-b:b=1)]

This one simply changes the type of the second comparison in the first 'OR' to 'type-a', so that both types in that 'OR' are the same. If the first example is okay, this one should be too.