Upgrade arc-xcode-test-engine to v3.0.3.
Upgrade arc-xcode-test-engine to v3.0.3.

Summary:
Resolves issues with Xcode 7.3 and arc unit's coverage reporting.

See the v3.0.3 release notes: https://github.com/google/arc-xcode-test-engine/releases/tag/v3.0.3

Reviewers: #mdc_ios_owners, ajsecord

Reviewed By: #mdc_ios_owners, ajsecord

Projects: #material_components_ios

Differential Revision: http://codereview.cc/D821

material-components/material-components-ios,willlarche/material-components-ios,willlarche/material-components-ios,sigito/material-components-ios,willlarche/material-components-ios,samnm/material-components-ios,chriscox/material-components-ios,samnm/material-components-ios,Eccelor/material-components-ios,randallli/material-components-ios,randallli/material-components-ios,samnm/material-components-ios,willlarche/material-components-ios,randallli/material-components-ios,chriscox/material-components-ios,chriscox/material-components-ios,Eccelor/material-components-ios,material-components/material-components-ios,brianjmoore/material-components-ios,randallli/material-components-ios,samnm/material-components-ios,randallli/material-components-ios,brianjmoore/material-components-ios,sigito/material-components-ios,sigito/material-components-ios,Eccelor/material-components-ios,randallli/material-components-ios,material-components/material-components-ios,chriscox/material-components-ios,willlarche/material-components-ios,material-components/material-components-ios,sigito/material-components-ios,brianjmoore/material-components-ios,samnm/material-components-ios,material-components/material-components-ios,chriscox/material-components-ios,sigito/material-components-ios,brianjmoore/material-components-ios,brianjmoore/material-components-ios,Eccelor/material-components-ios,Eccelor/material-components-ios