Fix incorrect value for "strategy" with deflateParams() in walmethods.c

The zlib documentation mentions the values supported for the compression
strategy, but this code has been using a hardcoded value of 0 rather
than Z_DEFAULT_STRATEGY.  This commit adjusts the code to use
Z_DEFAULT_STRATEGY.

Backpatch down to where this code has been added to ease the backport of
any future patch touching this area.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/1400032.1662217889@sss.pgh.pa.us
Backpatch-through: 10

src/bin/pg_basebackup/walmethods.c

@@ -706,7 +706,7 @@ tar_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_
 			return NULL;
 
 		/* Turn off compression for header */
-		if (deflateParams(tar_data->zp, 0, 0) != Z_OK)
+		if (deflateParams(tar_data->zp, 0, Z_DEFAULT_STRATEGY) != Z_OK)
 		{
 			tar_set_error("could not change compression parameters");
 			return NULL;
@@ -746,7 +746,8 @@ tar_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_
 			return NULL;
 
 		/* Re-enable compression for the rest of the file */
-		if (deflateParams(tar_data->zp, tar_data->compression, 0) != Z_OK)
+		if (deflateParams(tar_data->zp, tar_data->compression,
+						  Z_DEFAULT_STRATEGY) != Z_OK)
 		{
 			tar_set_error("could not change compression parameters");
 			return NULL;
@@ -960,7 +961,7 @@ tar_close(Walfile f, WalCloseMethod method)
 	else
 	{
 		/* Turn off compression */
-		if (deflateParams(tar_data->zp, 0, 0) != Z_OK)
+		if (deflateParams(tar_data->zp, 0, Z_DEFAULT_STRATEGY) != Z_OK)
 		{
 			tar_set_error("could not change compression parameters");
 			return -1;
@@ -972,7 +973,8 @@ tar_close(Walfile f, WalCloseMethod method)
 			return -1;
 
 		/* Turn compression back on */
-		if (deflateParams(tar_data->zp, tar_data->compression, 0) != Z_OK)
+		if (deflateParams(tar_data->zp, tar_data->compression,
+						  Z_DEFAULT_STRATEGY) != Z_OK)
 		{
 			tar_set_error("could not change compression parameters");
 			return -1;