Use RenderTestBase.createParserFromPath for layout files

LayoutPullParser.createFromPath seems not to be able to handle paths
starting with "./" when running tests from the command line as on
buildbot.

Bug: N/A
Test: RenderTests.testShadowFlagsNoShadows
Change-Id: I17753a3cac7c665e6f112c6d1d8bca7019160b2c
(cherry picked from commit e7caa8d887e41b2c52eaae2ef520fd2033c279f0)