chore: improve pg init container scripts (#2463)

Author: ldming

addons/postgresql/scripts/init_container.sh

@@ -20,6 +20,11 @@ cp "$postgres_template_conf_file" "$postgres_conf_dir"
 chmod 755 "$postgres_conf_dir"
 chmod 664 "$postgres_conf_file"
 
-# Copy wal-g binary
-mkdir -p "$postgres_walg_dir"
-cp /spilo-init/bin/wal-g ${postgres_walg_dir}/wal-g
+# Copy wal-g binary if it exists, the wal-g-archive backup use the spilo image,
+# so we need to copy the wal-g binary to the spilo image.
+# Why wal-g-archive backup use the spilo image instead of the walg image?
+# Because the wal-g-archive uses the pg_waldump binary, which is not in the walg image.
+if [ -f /spilo-init/bin/wal-g ]; then
+    mkdir -p "$postgres_walg_dir"
+    cp /spilo-init/bin/wal-g ${postgres_walg_dir}/wal-g
+fi