Must check indisready not just indisvalid when dumping from 9.2 server.

9.2 uses a kluge representation of "indislive"; we have to account for
that when examining pg_index.  Simplest solution is to check indisready
for 9.0 and 9.1 as well; that's harmless though unnecessary, so it's
not worth making a version distinction for.

Fixes oversight in commit 683abc73,
as noted by Andres Freund.