Add group-related workload
Add group-related workload

This patch further extends the RAPI workload by exercising all the
group-related functionality.

Signed-off-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

andir/ganeti,dimara/ganeti,apyrgio/ganeti,andir/ganeti,mbakke/ganeti,andir/ganeti,ganeti/ganeti,mbakke/ganeti,ganeti/ganeti,yiannist/ganeti,mbakke/ganeti,bitemyapp/ganeti,apyrgio/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti/ganeti,leshchevds/ganeti,onponomarev/ganeti,grnet/snf-ganeti,leshchevds/ganeti,ganeti-github-testing/ganeti-test-1,ganeti-github-testing/ganeti-test-1,dimara/ganeti,bitemyapp/ganeti,onponomarev/ganeti,grnet/snf-ganeti,yiannist/ganeti