COMP: Fix initial configuration as a Remote Module.

When configured from the command line as a Remote Module on the initial CMake
configuration, ITKConfig.cmake does not exist until after the first successful
configuration pass. Return prematurely in this case so ITK_DIR/ITKConfig.cmake
will be found on subsequent CMake passes.
Merge pull request #2 from thewtex/RemoteConfiguration

COMP: Fix initial configuration as a Remote Module.