QUICNetVC crashes on active timeout

[maskit]

Logs from the QUIC test server running draft-29. This may happen on 9.0 (draft-27).

[Jul 24 10:12:17.080] [ET_NET 7] DEBUG: <QUICNetVConnection.cc:2215 (_switch_to_draining_st> (quic_net            ) [790cc548-29a85b33] Reason: Idle Timeout
[Jul 24 10:12:17.081] [ET_NET 7] DEBUG: <QUICNetVConnection.cc:2028 (_unschedule_ack_manage> (quic_net            ) [790cc548-29a85b33] Unschedule QUIC_EVENT_ACK_PERIODIC event
[Jul 24 10:12:17.081] [ET_NET 7] DEBUG: <QUICNetVConnection.cc:2227 (_switch_to_draining_st> (quic_net            ) [790cc548-29a85b33] Enter state_connection_draining
[Jul 24 10:12:17.081] [ET_NET 7] DEBUG: <QUICNetVConnection.cc:2003 (_schedule_closing_time> (quic_net            ) [790cc548-29a85b33] Schedule QUIC_EVENT_CLOSING_TIMEOUT event i
n 1616470ms
[Jul 24 10:12:18.076] [ET_NET 7] DEBUG: <QUICNetVConnection.cc:971 (state_connection_draini> (quic_net            ) [790cc548-29a85b33] Unexpected event: UNKNOWN (106)
Fatal: QUICNetVConnection.cc:972: failed assertion `false`

traffic_server: received signal 6 (Aborted)
traffic_server - STACK TRACE: 
/opt/ats/lib/libtscore.so.10(_Z20signal_crash_handleriP9siginfo_tPv+0x18)[0x7f95067c6d18]
/opt/ats/bin/traffic_server(_Z19crash_logger_invokeiP9siginfo_tPv+0x168)[0x78a5b0]
/lib64/libpthread.so.0(+0x12080)[0x7f9504e61080]
/lib64/libc.so.6(gsignal+0x10b)[0x7f9503f83eab]
/lib64/libc.so.6(abort+0x123)[0x7f9503f6e5b9]
/opt/ats/lib/libtscore.so.10(_Z11ink_warningPKcz+0x0)[0x7f950676b396]
/opt/ats/lib/libtscore.so.10(+0x202fc3)[0x7f9506762fc3]
/opt/ats/bin/traffic_server(_ZN18QUICNetVConnection25state_connection_drainingEiP5Event+0x4c2)[0xebcb24]
/opt/ats/bin/traffic_server(_ZN12Continuation11handleEventEiPv+0x19e)[0x796936]
/opt/ats/bin/traffic_server(_ZN18UnixNetVConnection8callbackEiPv+0x28)[0xe1c6d2]
/opt/ats/bin/traffic_server(_ZN13InactivityCop16check_inactivityEiP5Event+0xe90)[0xe7a540]
/opt/ats/bin/traffic_server(_ZN12Continuation11handleEventEiPv+0x19e)[0x796936]
/opt/ats/bin/traffic_server(_ZN7EThread13process_eventEP5Eventi+0x331)[0xf6d633]
/opt/ats/bin/traffic_server(_ZN7EThread15execute_regularEv+0x720)[0xf6e476]
/opt/ats/bin/traffic_server(_ZN7EThread7executeEv+0x2e9)[0xf6f0cb]
/opt/ats/bin/traffic_server[0xf6b9a0]
/lib64/libpthread.so.0(+0x7594)[0x7f9504e56594]
/lib64/libc.so.6(clone+0x3f)[0x7f9504046f4f]