build/android/install_emulator_deps.py: run kvm-ok as root when needed.

This change runs kvm-ok as root after installing the kvm and qemu-kvm
packages to ensure that KVM can work. This gives better diagnostics in
case of failure, which can happen for one of the following reasons:

  - The CPU doesn't support virtualization extensions.
  - The extensions have been disabled by the BIOS.

BUG=NONE
R=yfriedman@chromium.org,navabi@chromium.org,tfarina@chromium.org,raphael.kubo.da.costa@intel.com

Review URL: https://codereview.chromium.org/116493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241708 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241708