mysqld hangs on shutdown waiting for galera service thread

1. Bootstrap a 3-node galera cluster.
2. Stop bootstrap node (no clients connected, no transactions in progress)

mysqld sometimes hangs indefinitely on shutdown

150225 16:02:21 [Note] /usr/sbin/mysqld: Normal shutdown

150225 16:02:21 [Note] WSREP: Stop replication
150225 16:02:23 [Note] WSREP: rollbacker thread exiting
150225 16:02:23 [Note] Event Scheduler: Purging the queue. 0 events
150225 16:02:43 [Warning] /usr/sbin/mysqld: Forcing close of thread 26 user: ''

Thread 26 (Thread 0x7fec93bb2700 (LWP 11840)):
#0 0x00007feca06a15bc in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x00007fec9bd5962b in wait (arg=0x7fec9cd54320) at galerautils/src/gu_lock.hpp:56
#2 galera::ServiceThd::thd_func (arg=0x7fec9cd54320) at galera/src/galera_service_thd.cpp:30
#3 0x00007feca069d9d1 in start_thread () from /lib64/libpthread.so.0
#4 0x00007fec9edb78fd in clone () from /lib64/libc.so.6