Avoid false drops in query

[azizkayumov]

False drops of points in query may happen in random tests because of floating point round off errors. From the original SRTree source code (HnSRTreeNodeObject.cc):

		/*
		* NOTE:
		*
		*    Dec.13,2000 Norio KATAYAMA
		*
		*    Here ``getUpperBoundMaxDistance()'' is used for spheres
		*    in order to prevent false drops caused by round-off
		*    errors. As for rectangles, it is not necessary to use
		*    ``getUpperBoundMaxDistance()'' because the distance
		*    obtained by ``getMaxDistance()'' is guaranteed to be
		*    equal to or greater than the distance to the farthest
		*    point.
		*
		* Additional Note:
		*
		*    The above comment is satisfied only when the distance to
		*    a point is always measured by ``getDistance()'' and when
		*    bounding rectangles have the same precision with points.
		*    It is better to use ``getUpperBoundMaxDistance()'' instead
		*    of ``getMaxDistance()''.
		*/