[cros] Fix udevadm command line for camera presence detection.

Also added an overload of GetAppOutput which takes argv directly instead of CommandLine for launching programs where specific order of argument matters (like udevadm).

BUG=124845
TEST=Manual


Review URL: http://codereview.chromium.org/10191019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@134149 0039d316-1c4b-4281-b951-d872f2087c98

• base/process_util.h[diff]
• base/process_util_posix.cc[diff]
• chrome/browser/chromeos/login/camera_detector.cc[diff]
• chrome/browser/chromeos/system/name_value_pairs_parser.cc[diff]
• chrome/browser/chromeos/system/udev_info_provider.cc[diff]