netperf: introduce an agent to launch client sessions

Currently we use many threads/heavy control sessions to launch many
clients, Autotest takes too much of the host resources.

This patch introduces an agent script, it'll be executed inside the
client system to launch multiple sessions, and Autotest only needs
to use one background thread to control clients.

We can consider to process the raw results in this agent script in
future, if it can help to simplify the case.

Signed-off-by: Amos Kong <akong@redhat.com>
utils_misc: Add a function to normalize the data size

Normalize a data size in one order of magnitude to another (MB to GB,
for example). In this function you can also change the factor as you
need, the default factor is 1024.

changes from v1:
  - rename the function and variables
  - update the method for getting a fraction.
  - Add unittests

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
qemu/cfg/tests-example.cfg: Update examples to use current Fedora

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>