pgsql: Report waiting via PS while recovery is waiting for buffer pin i

Report waiting via PS while recovery is waiting for buffer pin in hot standby.

Previously while the startup process was waiting for the recovery conflict
with snapshot, tablespace or lock to be resolved, waiting was reported in
PS display, but not in the case of recovery conflict with buffer pin.
This commit makes the startup process in hot standby report waiting via PS
while waiting for the conflicts with other backends holding buffer pins to
be resolved.

Author: Masahiko Sawada
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/CA+fd4k4mXWTwfQLS3RPwGr4xnfAEs1ysFfgYHvmmoUgv6Zxvmg@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/64638ccba3a659d8b8a3a4bc5b47307685a64a8a

Modified Files
--------------
src/backend/storage/buffer/bufmgr.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)