rip out hid_serv_acting_as_directory()

When we made HidServDirectoryV2 always 1, we removed the situation
where a relay could choose not to be an HSDir. Now simplify the
rest of the code to reflect this decision.

(We have to remove two apparently unrelated free() calls in the unit
tests, since they used to free stuff that we created as a side effect
of calling router_get_my_routerinfo(), and now we no longer call that.)

src/test/test_rendcache.c

@@ -454,11 +454,6 @@ test_rend_cache_store_v2_desc_as_dir(void *data)
 
   rend_cache_init();
 
-  // Test when we are not an HS dir
-  mock_routerinfo = NULL;
-  ret = rend_cache_store_v2_desc_as_dir("");
-  tt_int_op(ret, OP_EQ, RCS_NOTDIR);
-
   // Test when we can't parse the descriptor
   mock_routerinfo = tor_malloc(sizeof(routerinfo_t));
   ret = rend_cache_store_v2_desc_as_dir("unparseable");