osd/OSD: fix build_past_intervals_parallel

We may be only calculating older past intervals and have a valid
history.same_interval_since value, in which case the local
same_interval_since value will end at the newest old interval we had to
generate.

Same as 0830275 change in generate_past_intervals()
This was introduced by 7031654.

Signed-off-by: David Zafman <dzafman@redhat.com>
(cherry picked from commit 0fd674b)

src/osd/OSD.cc

@@ -3080,10 +3080,7 @@ void OSD::build_past_intervals_parallel()
     PG *pg = i->first;
     pistate& p = i->second;
 
-    // Verify same_interval_since is correct
-    if (pg->info.history.same_interval_since) {
-      assert(pg->info.history.same_interval_since == p.same_interval_since);
-    } else {
+    if (pg->info.history.same_interval_since == 0) {
       assert(p.same_interval_since);
       dout(10) << __func__ << " fix same_interval_since " << p.same_interval_since << " pg " << *pg << dendl;
       dout(10) << __func__ << " past_intervals " << pg->past_intervals << dendl;