Revert "Merge pull request #4221 from openscholar/4215"

This reverts commit 65ed0f153d986a1509ae21ab6196f69508ee0cbb, reversing
changes made to 95e56db27c9351b50aee914b1bc1bf56446bce41.
Merge branch 'SCHOLAR-3.x' into 4215-proper
Prefix Overlay's Ajax callback with our PURL.
PURLify the ajax callback URL.
Merge pull request #4360 from openscholar/4215-proper

Prefix Overlay's Ajax callback with our PURL