services/identity: add discharger location
services/identity: add discharger location

I missed the OauthBlessingHandler in v.io/c/19335

Change-Id: I5cb665e6b312a7eff59504060543c4ddbb5ed91a

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref