Concurrently with partitioned index development (commit 8b08f7d4),
the code to handle failure to rename indexes was refactored (commit
8b9e9644).  Turns out that that particular case was untested, which
naturally led it to be broken.  Add tests and the missing code line.
Co-authored-by: David Rowley <dgrowley@gmail.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com>
Discussion: https://postgr.es/m/CAKcux6mfYMS3OX0ywjOiWiGSEKhJf-1zdeTceHFbd0mScUzU5A@mail.gmail.com