tools/rados: just return instead of exit(1) in "rados cppool" handler

Otherwise an occasional segfault occurs.  This instance was missed in
commit 2c14926 ("tools/rados: always call rados.shutdown() before
exit()").

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit de66355)

src/tools/rados/rados.cc

@@ -3133,7 +3133,7 @@ static int rados_tool_common(const std::map < std::string, std::string > &opts,
 	cerr << "    If you insist on making a broken copy, you can pass\n"
 	     << "    --yes-i-really-mean-it to proceed anyway."
 	     << std::endl;
-	exit(1);
+	return 1;
       }
     }