osd/osd_types: fix pg_pool_t encoding for hammer

If we are missing the hammer feature, we will also be missing the
luminous feature, but we should still encode like hammer.

Analogous fix to e28e0c6

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 37c22b2)

src/osd/osd_types.cc

@@ -1543,8 +1543,7 @@ void pg_pool_t::encode(bufferlist& bl, uint64_t features) const
     // this was the first post-hammer thing we added; if it's missing, encode
     // like hammer.
     v = 21;
-  }
-  if (!HAVE_FEATURE(features, SERVER_LUMINOUS)) {
+  } else if (!HAVE_FEATURE(features, SERVER_LUMINOUS)) {
     v = 24;
   }