tests: auto-generate random addresses instead of hard-coding them

The main benefit is that there is less manual work to add a
test (discovery of unique random addresses is not necessary),
but it also ensures that the tests can run on environments where the
previously hard-coded addresses were present.

Signed-off-by: Nikos Mavrogiannopoulos <n.mavrogiannopoulos@gmail.com>

tests/radius-config

@@ -94,8 +94,7 @@ function wait_file_contents {
 }
 
 # server address
-ADDRESS=10.102.246.1
-CLI_ADDRESS=10.102.247.1
+. `dirname $0`/random-net.sh
 
 # These addresses must match the radius sent ranges
 VPNNET=192.168.66.0/24