[crosutils] Remove --use_emerged from cros_run_parallel_vm_tests
[crosutils] Remove --use_emerged from cros_run_parallel_vm_tests

cros_run_parallel_vm_tests doesn't work unless you pass --use_emerged; there must be some underlying issue with trying to perform multiple run_remote_tests commands at the same time, even on different VMs.  So, remove the option and force --use_emerged on the calls to cros_run_vm_test.

BUG=8544
TEST=run two tests in parallel with cros_run_parallel_vm_tests and see that they both complete.

Change-Id: I1152ca3dd7f1de37261da894b9b903c90c2e6524

Review URL: http://codereview.chromium.org/6612058

marineam/coreos-scripts,fivethreeo/scripts,marineam/coreos-scripts,BugRoger/scripts,mischief/scripts,crawford/scripts,bcwaldon/coreos-scripts,trnubo/scripts,sigma/coreos-scripts,gtank/scripts,mjg59/scripts,zhang0137/scripts,crawford/scripts,nicescale/scripts,gtank/scripts,endocode/scripts,trnubo/scripts,gtank/scripts,nicescale/scripts,zhang0137/scripts,andrejro/coreos--scripts,smilart/scripts,andrejro/coreos--scripts,smilart/scripts,fivethreeo/scripts,coreos/scripts,bcwaldon/coreos-scripts,vmware/coreos-scripts,glevand/coreos--scripts,sigma/coreos-scripts,coreos/scripts,mischief/scripts,BugRoger/scripts,zhang0137/scripts,endocode/scripts,mjg59/scripts,nicescale/scripts,sigma/coreos-scripts,andrejro/coreos--scripts,vmware/coreos-scripts,endocode/scripts,marineam/coreos-scripts,mjg59/scripts,vmware/coreos-scripts,crawford/scripts,mischief/scripts,BugRoger/scripts,fivethreeo/scripts,bcwaldon/coreos-scripts,smilart/scripts,glevand/coreos--scripts,trnubo/scripts