Rename connection_free_ to connection_free_minimal.

src/or/connection.c

src/or/connection.h

src/test/test_dir_handle_get.c

src/test/test_entryconn.c

src/test/test_extorport.c

src/test/test_hs_cache.c

src/test/test_hs_client.c

src/test/test_link_handshake.c

src/test/test_oom.c

src/test/test_routerlist.c