pgsql: Fix WAL file selection in 013_rewind test

Fix WAL file selection in 013_rewind test

Without an explicit WAL filename, pg_waldump determines the segment
size from the first WAL-named directory entry. A preallocated
segment with an uninitialized header can make this fail before the
checkpoint is read.

Pass the WAL filename recorded in backup_label to avoid depending
on directory enumeration order. Use command_like() so command
failures and stderr are checked rather than appearing only as an
empty-output mismatch.

This was independently reported by Nazir Bilal Yavuz and Alexander
Lakhin.

Author: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Reported-by: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Reported-by: Alexander Lakhin <exclusion(at)gmail(dot)com>
Reviewed-by: Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://postgr.es/m/CAN55FZ1Yak_xBqMaDQsD7atpBkGLEkF-DKXcs3nLHM1Uq4YRew%40mail.gmail.com
Discussion: https://postgr.es/m/ffd837c5-dc22-4db1-a2d8-b623cbe9b30c@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a5447a2deaca65c69f1838240f6bdb3ff85c9577

Modified Files
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src/test/modules/test_checksums/t/013_rewind.pl | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)