libceph: return primary from ceph_calc_pg_acting()

In preparation for adding support for primary_temp, stop assuming
primaryness: add a primary out parameter to ceph_calc_pg_acting() and
change call sites accordingly.  Primary is now specified separately
from the order of osds in the set.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 6f64eec..b4157dc 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1333,7 +1333,7 @@
 {
 	struct ceph_pg pgid;
 	int acting[CEPH_PG_MAX_SIZE];
-	int o = -1, num = 0;
+	int num, o;
 	int err;
 	bool was_paused;
 
@@ -1346,11 +1346,9 @@
 	}
 	req->r_pgid = pgid;
 
-	err = ceph_calc_pg_acting(osdc->osdmap, pgid, acting);
-	if (err > 0) {
-		o = acting[0];
-		num = err;
-	}
+	num = ceph_calc_pg_acting(osdc->osdmap, pgid, acting, &o);
+	if (num < 0)
+		num = 0;
 
 	was_paused = req->r_paused;
 	req->r_paused = __req_should_be_paused(osdc, req);