bugfix: fix UE realtime bug
When pushing traffic with iperf the UE was crashing.
The argument passed to pthread_mutex_timedlock is absolute time based on the CLOCK_REALTIME timer, not relative time. That seems to be the root cause of the bug. (That there is a timeout is another story.)
This commit uses absolute value.
Also we separate cases between IS_SOFTMODEM_BASICSIM / IS_SOFTMODEM_RFSIM and standard realtime UE. In the 'sim' modes we don't care about timeout and just call pthread_mutex_lock. It seems to be the idea of the original work. If not, then to be fixed.