pgsql: Log a message when resorting to SIGKILL during shutdown/crash re

Log a message when resorting to SIGKILL during shutdown/crash recovery.

Currently, no useful trace is left in the logs when the postmaster
is forced to use SIGKILL to shut down children that failed to respond
to SIGQUIT.  Some questions were raised about how often that scenario
happens in the buildfarm, so let's add a LOG-level message showing
that it happened.

Discussion: https://postgr.es/m/1850884.1599601164@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/10095ca634fb39d78cfae8000489a19f4f4e27ef

Modified Files
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src/backend/postmaster/postmaster.c | 2 ++
1 file changed, 2 insertions(+)