Mark yang generated source location as a source directory.
Mark yang generated source location as a source directory.

Change-Id: I958affa226e9e34a795ffea42450976ca9ef4697
Signed-off-by: Nathan Harmon <2c8949a42dbaa969136421f402764168b862bfaa@hp.com>

opendaylight/yangtools,NovusTheory/yangtools,opendaylight/yangtools,522986491/yangtools