memory leaks in new channel code
```
==2387== 104 bytes in 1 blocks are definitely lost in loss record 21 of 39
==2387== at 0x4C244E8: malloc (vg_replace_malloc.c:236)
==2387== by 0x2259F7: _tor_malloc (util.c:144)
==2387== by 0x227035: _tor_malloc_zero (util.c:170)
==2387== by 0x18DE19: channel_tls_start_listener (channeltls.c:190)
==2387== by 0x1D4B54: connection_tls_start_handshake (connection_or.c:1201)
==2387== by 0x1C48E7: connection_handle_listener_read (connection.c:1303)
==2387== by 0x1C52E4: connection_handle_read (connection.c:2689)
==2387== by 0x11CB90: conn_read_callback (main.c:720)
==2387== by 0x52C9343: event_base_loop (in /usr/lib/libevent-1.4.so.2.1.3)
==2387== by 0x11A510: do_main_loop (main.c:1986)
==2387== by 0x11A8CC: tor_main (main.c:2694)
==2387== by 0x5EFCC8C: (below main) (libc-start.c:228)
==2387==
```
```
==2387== 672 (56 direct, 616 indirect) bytes in 1 blocks are definitely lost in loss record 29 of 39
==2387== at 0x4C244E8: malloc (vg_replace_malloc.c:236)
==2387== by 0x2259F7: _tor_malloc (util.c:144)
==2387== by 0x227035: _tor_malloc_zero (util.c:170)
==2387== by 0x1A220E: circuitmux_alloc (circuitmux.c:361)
==2387== by 0x18E153: channel_tls_connect (channeltls.c:132)
==2387== by 0x19795B: circuit_handle_first_hop (circuitbuild.c:159)
==2387== by 0x19A796: circuit_establish_circuit (circuitbuild.c:1957)
==2387== by 0x1AB0C2: circuit_launch_by_extend_info (circuituse.c:1364)
==2387== by 0x1ACD9D: circuit_build_needed_circs (circuituse.c:741)
==2387== by 0x11DBBD: second_elapsed_callback (main.c:1495)
==2387== by 0x52C9343: event_base_loop (in /usr/lib/libevent-1.4.so.2.1.3)
==2387== by 0x11A510: do_main_loop (main.c:1986)
```
```
==2387== 1,344 (112 direct, 1,232 indirect) bytes in 2 blocks are definitely lost in loss record 35 of 39
==2387== at 0x4C244E8: malloc (vg_replace_malloc.c:236)
==2387== by 0x2259F7: _tor_malloc (util.c:144)
==2387== by 0x227035: _tor_malloc_zero (util.c:170)
==2387== by 0x1A220E: circuitmux_alloc (circuitmux.c:361)
==2387== by 0x18E153: channel_tls_connect (channeltls.c:132)
==2387== by 0x19795B: circuit_handle_first_hop (circuitbuild.c:159)
==2387== by 0x19A796: circuit_establish_circuit (circuitbuild.c:1957)
==2387== by 0x1AB0C2: circuit_launch_by_extend_info (circuituse.c:1364)
==2387== by 0x1ACA39: circuit_build_needed_circs (circuituse.c:711)
==2387== by 0x11DBBD: second_elapsed_callback (main.c:1495)
==2387== by 0x52C9343: event_base_loop (in /usr/lib/libevent-1.4.so.2.1.3)
==2387== by 0x11A510: do_main_loop (main.c:1986)
```
on a normal relay
issue