Post-push fix for Bug#20691930 (innodb_zip.wl5522_debug_zip failure):

Do not attempt to reset the page type when importing compressed tablespaces.
The page type can be invalid only on uncompressed tablespaces, because
at the time when compression support was introduced, InnoDB already
initialized FIL_PAGE_TYPE on every page.

(cherry picked from commit 8823190d8898a0d02ebeae1cb4906550f788660c)

Author: Marko Mäkelä

storage/innobase/row/row0import.cc

@@ -2085,7 +2085,7 @@ PageConverter::operator() (
 		    || fil_page_type_is_index(page_type)) {
 
 			buf_flush_init_for_writing(
-				block,
+				!is_compressed_table() ? block : NULL,
 				!is_compressed_table()
 				? block->frame : block->page.zip.data,
 				!is_compressed_table() ? 0 : m_page_zip_ptr,