Segfault race when shutting down in log server

Thread 2 (Thread 0x7f4daa480740 (LWP 104777)):

#0  0x000000317680859d in pthread_join () from /lib64/libpthread.so.0

#1  0x0000000000440db5 in __wt_thread_join (session=0x11b9d30, tid=139971485144832)

    at ../src/os_posix/os_thread.c:37

#2  0x00000000004bd282 in __wt_logmgr_destroy (session=0x11b9d30) at ../src/conn/conn_log.c:867

#3  0x0000000000417b10 in __wt_connection_close (conn=0x119c260) at ../src/conn/conn_open.c:140

#4  0x0000000000410e1b in __conn_close (wt_conn=0x119c260, config=0x0)

    at ../src/conn/conn_api.c:1004

#5  0x000000000040c074 in wts_close () at ../../../test/format/wts.c:446

#6  0x0000000000409837 in main (argc=0, argv=0x7ffd8e8f9910) at ../../../test/format/t.c:238

Thread 1 (Thread 0x7f4da6a69700 (LWP 106541)):

#0  0x000000000043e91a in __wt_cond_signal (session=0x11baf30, cond=0x0)

    at ../src/os_posix/os_mtx_cond.c:125

#1  0x00000000004bc584 in __wt_log_wrlsn (session=0x11baf30) at ../src/conn/conn_log.c:560

#2  0x00000000004bc678 in __log_wrlsn_server (arg=0x11baf30) at ../src/conn/conn_log.c:595

#3  0x0000003176807555 in start_thread () from /lib64/libpthread.so.0

#4  0x0000003176502b9d in clone () from /lib64/libc.so.6