travis: use libfreeradius-client-dev instead of radiusclient-ng

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@11046 ddefafc4-47db-0310-ae44-fa13212b10f2
travis: add libsrtp-dev, required for recon build

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/main@11047 ddefafc4-47db-0310-ae44-fa13212b10f2