Fix intermittent failures invoking SimLauncher::Simulator::xcode_version
- “xcodebuild -version” will intermittently have a non-zero exit on success, so detect failure via parsing exceptions
- remove call to xcode_version for iphonesim_path as it’s unused
Merge pull request #25 from jtomson-mdsol/fix_xcode_version_invocation

Fix intermittent failures invoking SimLauncher::Simulator::xcode_version