crush: decode and initialize chooseleaf_vary_r

Commit e2b149c ("crush: add chooseleaf_vary_r tunable") added the
crush_map::chooseleaf_vary_r field but missed the decode part.  This
lead to misdirected requests caused by incorrect raw crush mapping
sets.

Fixes: http://tracker.ceph.com/issues/8226

Reported-and-Tested-by: Dmitry Smirnov <onlyjob@member.fsf.org>
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

net/ceph/osdmap.c

@@ -329,6 +329,11 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
 	dout("crush decode tunable chooseleaf_descend_once = %d",
 	     c->chooseleaf_descend_once);
 
+	ceph_decode_need(p, end, sizeof(u8), done);
+	c->chooseleaf_vary_r = ceph_decode_8(p);
+	dout("crush decode tunable chooseleaf_vary_r = %d",
+	     c->chooseleaf_vary_r);
+
 done:
 	dout("crush_decode success\n");
 	return c;