add copy of MyFamily element to the descriptor, not the element itself

If we add the element itself, we will later free it when we free the
descriptor, and the next time we go to look at MyFamily, things will
go badly.

Fixes the rest of bug 22368; bugfix on 0.3.1.1-alpha.

src/or/router.c

@@ -2308,7 +2308,7 @@ router_build_fresh_descriptor(routerinfo_t **r, extrainfo_t **e)
            smartlist_add_strdup(warned_nonexistent_family, name);
          }
          if (is_legal) {
-           smartlist_add(ri->declared_family, name);
+           smartlist_add_strdup(ri->declared_family, name);
            name = NULL;
          }
        } else if (router_digest_is_me(member->identity)) {