pgsql: Fix subscriber invalid memory access on DDL.

Fix subscriber invalid memory access on DDL.

This patch allows building the local relmap cache for a subscribed
relation after processing pending invalidation messages and potential
relcache updates.  Without this, the attributes in the local cache don't
tally with the updated relcache entry leading to invalid memory access.

Reported-by Jehan-Guillaume de Rorthais
Author: Jehan-Guillaume de Rorthais and Vignesh C
Reviewed-by: Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/20191025175929.7e90dbf5@firost

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/04c8a69c0cccbc271e0feeb22a74c69fbd87c37e

Modified Files
--------------
src/backend/replication/logical/relation.c | 38 ++++++++++++++++++++----------
1 file changed, 25 insertions(+), 13 deletions(-)