Fix: remove assertions in lttng-ust-comm init

Assertions in the lttng-ust-comm init function are slightly too harsh
for their own good. In situations involving incoherent seccomp profiles
(e.g. accepting futex, poll, nanosleep, clock_nanosleep, but not
restart_syscall), unexpected errno values can be returned by
sem_timedwait.

Print an error in those situations, but let the application proceed.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>