rose suite-run: validate in strict mode.

Applies to the suite engine configuration only.
Merge branch 'master' into 54.suite-run.validate.strict
Merge branch 'master' into 54.suite-run.validate.strict
Merge branch 'master' into 54.suite-run.validate.strict
Merge branch 'master' into 54.suite-run.validate.strict
Minor logic improvement and comment fix.
Merge pull request #422 from matthewrmshin/54.suite-run.validate.strict

rose suite-run: validate in strict mode.
rose task-run --path=PATH: expand tilde in PATH.
Merge pull request #430 from matthewrmshin/rose-task-run--path=tilde

rose task-run --path=PATH: expand tilde in PATH.
rose task-run: allow empty site/user configuration.
Merge pull request #433 from matthewrmshin/rose-task-run.no-conf

rose task-run: allow empty site/user configuration.