For operations where there is both a source and destination resource, set the number of transfer threads to the smaller number as defined by the acSetNumThreads policy.

Signed-off-by: Chris Smith <chris@distributedbio.com>

git-svn-id: svn://irodssvn.ucsd.edu/trunk@5394 ea137bd6-aa86-47b6-b90d-b101d9f19a90