improve handling of single family chain filters

We currently support non equality qualifier filters when exactly one family is specified in the scan:

```java
Scan s = new Scan();
s.addFamily("f".getBytes());
s.setFilter(
new FilterList(
new QualifierFilter(CompareOp.NOT_EQUAL, new BinaryComparator("q".getBytes())),
new QualifierFilter(CompareOp.NOT_EQUAL, new BinaryComparator("q2".getBytes()))
)
);
```

However we don't support:
```java
Scan s = new Scan();
s.setFilter(
new FilterList(
new FamilyFilter(CompareOp.EQUAL, new BinaryComparator("f".getBytes())),
new QualifierFilter(CompareOp.NOT_EQUAL, new BinaryComparator("q".getBytes())),
new QualifierFilter(CompareOp.NOT_EQUAL, new BinaryComparator("q2".getBytes()))
)
);
```
Which should be equivalent.