MDEV-21549 IMPORT TABLESPACE fails to adjust all tablespace ID in root pages

After MDEV-12353, the consistency check that I originally added for
commit 1b9fe0bb
(InnoDB Plugin for MySQL 5.1) started randomly failing.

It turns out that the IMPORT TABLESPACE code was always incorrect:
it did not update the (redundantly stored) tablespace ID
in index tree root pages. It only does that for page headers
and BLOB pointers.

PageConverter::update_index_page(): Update the tablespace ID
in the BTR_SEG_TOP and BTR_SEG_LEAF of index root pages.

storage/innobase/row/row0import.cc

@@ -1902,6 +1902,23 @@ PageConverter::update_index_page(
 		return(DB_SUCCESS);
 	}
 
+	if (m_index && block->page.id.page_no() == m_index->m_page_no) {
+		byte *b = FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF + FSEG_HDR_SPACE
+			+ page;
+		mach_write_to_4(b, block->page.id.space());
+
+		memcpy(FIL_PAGE_DATA + PAGE_BTR_SEG_TOP + FSEG_HDR_SPACE
+		       + page, b, 4);
+		if (UNIV_LIKELY_NULL(block->page.zip.data)) {
+			memcpy(&block->page.zip.data[FIL_PAGE_DATA
+						     + PAGE_BTR_SEG_TOP
+						     + FSEG_HDR_SPACE], b, 4);
+			memcpy(&block->page.zip.data[FIL_PAGE_DATA
+						     + PAGE_BTR_SEG_LEAF
+						     + FSEG_HDR_SPACE], b, 4);
+		}
+	}
+
 #ifdef UNIV_ZIP_DEBUG
 	ut_a(!is_compressed_table()
 	     || page_zip_validate(m_page_zip_ptr, page, m_index->m_srv_index));