Description of problem:
posix_lookup triggers a gfid heal only of loc->inode->gfid is not null. But if a readdirp comes on the parent dir before the lookup, the inode is linked and the gfid never heals. 

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Apply http://review.gluster.org/#/c/10667/ and run `tests/basic/afr/data-self-heal.t`. Tests will fail because heal was not successful due to absence of 
the gfid hardlink


Expected results:
server readdirp must only link inodes  that have a valid gfid link.