adding free radius (sonic-net#21307)

Why I did it
In a subsequent PR in the sonic-mgmt repo, I will add RADIUS tests, and there needs to be a consumable RADIUS server in the infrastructure.

How I did it
Added the freeradius package the ptf docker j2 file.

How to verify it
I build the new docker image locally and then ran few succesfull app-topo tasks inside of sonic-mgmt. Also verifed that freeradius is installed.

Author: dt-nexthop

dockers/docker-ptf/Dockerfile.j2

@@ -91,7 +91,8 @@ RUN apt-get update          \
         gdb                 \
         automake            \
         iproute2            \
-        wireshark-common
+        wireshark-common    \
+        freeradius
 
 {% if PTF_ENV_PY_VER == "py3" %}
 RUN update-alternatives --install /usr/bin/python python /usr/bin/python3 1 \