The "<=" comparison operator for chunk/shard versions is incorrectly coded to execute a "<" comparison.

Limited testing suggests minimal impact; adding a "fatal assert" on the missed case (where the values compared are equal) showed that a test for reload failed, leading to unnecessary reloads, but did not reveal other symptoms.

For 2.5 and 2.4, the affected code is in src/mongo/s/chunk_version.h.
For 2.2, the affected code is in src/mongo/s/util.h.