run_net_test - further boost UML entropy

Per:
  https://android-build.googleplex.com/builds/submitted/5097760/kernel_test/latest/view/logs/build.log

we appear to still not have quite enough:
  ...
  random: fast init done
  adding entropy from hex string [fdf7357dcff34af28ec2ef7907fda944a9adbbd62e6d4cc4a4f36b0771bc1d75]
  ...
  ##### Found 23 tests.
  ##### ./csocket_test.py (1/23)
  random: csocket_test.py: uninitialized urandom read (16 bytes read)
  ...
  ##### ./bpf_test.py (10/23)
  ...
  random: bpf_test.py: uninitialized urandom read (16 bytes read)
  random: crng init done

(although I cannot reproduce it on my desktop)

Change-Id: I90a4d9f7a3433049a3a22f60ddb32f2875e250e4