pgsql: pg_upgrade: Test --check with a running source server

pg_upgrade: Test --check with a running source server

4fff78f009 has added coverage for pg_upgrade --check, but only after
stopping the source server. This adds coverage for the case where a
source server is still running, checking for port patterns and a success
case where the old server still runs.

The chdir() required for VPATH builds needs to be moved slightly
earlier, to adapt to the generation of the logs.

Author: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
Reviewed-by: Ewan Young <kdbase(dot)hack(at)gmail(dot)com>
Discussion: https://postgr.es/m/apU4/hmRv/4gv20W(at)bdtpg

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/88aa6ca138a1eaa63618b2e6ef85ca6c7422dfed

Modified Files
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src/bin/pg_upgrade/t/002_pg_upgrade.pl | 46 ++++++++++++++++++++++++++++++----
1 file changed, 41 insertions(+), 5 deletions(-)