Remove the postmaster.pid file prior to pgBackRest restore

This commit removes the postmaster.pid file, if it exists, from the PGDATA
directory before attempting a restore. This allows the restore to be tried
more than once without causing an error due to the presence of the file
in subsequent attempts or in scenarios where the file is otherwise present.

Issue: [sc-15157]

Author: tjmoore4

internal/pgbackrest/config.go

@@ -197,11 +197,16 @@ func RestoreCommand(pgdata string, args ...string) []string {
 	// - https://www.postgresql.org/docs/current/hot-standby.html
 	// - https://www.postgresql.org/docs/current/app-pgcontroldata.html
 
+	// The postmaster.pid file is removed, if it exists, before attempting a restore.
+	// This allows the restore to be tried more than once without the causing an
+	// error due to the presence of the file in subsequent attempts.
+
 	// The 'pg_ctl' timeout is set to a very large value (1 year) to ensure there
 	// are no timeouts when starting or stopping Postgres.
 
 	const restoreScript = `declare -r pgdata="$1" opts="$2"
 install --directory --mode=0700 "${pgdata}"
+rm -f "${pgdata}/postmaster.pid"
 eval "pgbackrest restore ${opts}"
 rm -f "${pgdata}/patroni.dynamic.json"
 export PGDATA="${pgdata}" PGHOST='/tmp'