deadlock in lttng_ust_init

Happens when running tests for https://code.launchpad.net/~dandrader/qtmir/content-hub-clipboard/+merge/303863 by CI.

This is the backtrace of where it gets stuck:
#0 0xffffffff in __pthread_mutex_unlock_usercnt (mutex=0xb6fff514 <_rtld_global+1220>, decr=1) at pthread_mutex_unlock.c:51
#1 0xffffffff in tls_get_addr_tail (ti=0xb637021c, dtv=0xb3757008, the_map=<optimized out>) at dl-tls.c:778
#2 0xffffffff in lttng_ust_init () at /usr/include/urcu/static/urcu-bp.h:158
#3 0xffffffff in lttng_ust_init () at lttng-ust-comm.c:369
#4 0xffffffff in lttng_ust_init () at lttng-ust-comm.c:1481
#5 0xffffffff in call_init (l=<optimized out>, argc=argc@entry=1, argv=argv@entry=0xbefff3d4, env=env@entry=0xbefff3dc) at dl-init.c:72
#6 0xffffffff in _dl_init (env=<optimized out>, argv=<optimized out>, argc=<optimized out>, l=<optimized out>) at dl-init.c:30
#7 0xffffffff in _dl_init (main_map=0xb6fff958, argc=1, argv=0xbefff3d4, env=0xbefff3dc) at dl-init.c:120
#8 0xffffffff in _dl_start_user () at /lib/ld-linux-armhf.so.3

It gets stuck during initialization, more specifically, inside lttng_fixup_urcu_bp_tls()