Handle fatal file system errors in SoSReport.collect()

Out-of-space and read-only file system errors from plugins
should be treated as fatal and cause the run to end.

Partial fix for Issue #266.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
Handle fatal file system errors in SoSReport.*report()

Out-of-space and read-only file system errors while writing the
XML, plain-text, or HTML reports should be treated as fatal and
cause the run to end.

Partial fix for Issue #266.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>