[MONDRIAN-1568] Fixing failure due to infinite loop while determining aggregate star.  Looking up the agg star when role-limited members are in context requires finding the set of accessible members in order
set the complete bitkey.  Determining those members when using a context constraint requires looking up the agg star.  To side-step the issue, set NonEmpty to false when looking for accessible members while
the constraintBitKey, which avoids use of a context constraint.
Merge pull request #106 from mkambol/mondrian-1568

[MONDRIAN-1568] Fixing failure due to infinite loop while determining aggregate star