pgsql: Make local copy of client hostnames in backend status array.

Make local copy of client hostnames in backend status array.

The other strings, application_name and query string, were snapshotted to
local memory in pgstat_read_current_status(), but we forgot to do that for
client hostnames. As a result, the client hostname would appear to change in
the local copy, if the client disconnected.

Backpatch to all supported versions.

Author: Edmund Horner
Reviewed-by: Michael Paquier
Discussion:
https://www.postgresql.org/message-id/CAMyN-kA7aOJzBmrYFdXcc7Z0NmW%2B5jBaf_m%3D_-77uRNyKC9r%3DA%40mail.gmail.com

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/74dc05e01e5a195e432c6bd31f6504eb24b8316b

Modified Files
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src/backend/postmaster/pgstat.c | 7 +++++++
1 file changed, 7 insertions(+)