Don't do expensive consensus stuff when not a cache.

This includes generating and storing compressed consensuses, and
consensus diffs.  Fixes bug 23275; bugfix on 0.3.1.1-alpha.

changes/bug23275

@@ -0,0 +1,5 @@
+  o Minor bugfixes (relay):
+    - When a relay is not running as a directory cache, it will no longer
+      generate compressed consensuses and consensus diff information.
+      Previously, this was a waste of disk and CPU.  Fixes bug 23275;
+      bugfix on 0.3.1.1-alpha.

src/or/main.c

@@ -1487,7 +1487,7 @@ run_scheduled_events(time_t now)
 
   /* 12. launch diff computations.  (This is free if there are none to
    * launch.) */
-  if (server_mode(options)) {
+  if (dir_server_mode(options)) {
     consdiffmgr_rescan();
   }
 }

src/or/networkstatus.c

@@ -2014,7 +2014,7 @@ networkstatus_set_current_consensus(const char *consensus,
                                                &c->digests,
                                                c->digest_sha3_as_signed,
                                                c->valid_after);
-    if (server_mode(get_options())) {
+    if (dir_server_mode(get_options())) {
       consdiffmgr_add_consensus(consensus, c);
     }
   }