Changes

osmo-gsm-tester: Allow setting rtprio inside the container
This fixes for instance srsLTE being unable to create a thread with 
realtime priority.
Change-Id: If0d033c6e912795804e6d7322c22fdfc6602028b

osmo-gsm-tester: Allow passing osmo-gsm-tester params from jenkins.sh
caller
After this patch, one can run osmo-gsm-tester with specific parameters
(debug level, suite and tests to run, etc.) by using 
OSMO_GSM_TESTER_OPTS variable: OSMO_GSM_TESTER_OPTS="-s 4g -t ping -l
error" ./jenkins.sh
Change-Id: I2e8ff51a3152125148c6a117a987e8c11a576e1e