pgsql: Fail BRIN control functions during recovery explicitly

Fail BRIN control functions during recovery explicitly

They already fail anyway, but prior to this patch they raise an ugly
error message about a lock that cannot be acquired.  This just improves
the message.

Author: Masahiko Sawada
Reported-by: Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoBZau4g4_NUf3BKNd=CdYK+xaPdtJCzvOC1TxGdTiJx_Q@mail.gmail.com
Reviewed-by: Kuntal Ghosh, Alexander Korotkov, Simon Riggs, Michaël Paquier, Álvaro Herrera

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e951f66deadbe78da83b2d1919d39883d098fdff

Modified Files
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src/backend/access/brin/brin.c | 6 ++++++
1 file changed, 6 insertions(+)