Fix code analysis warnings

[martincostello]

Fix code analysis issues/warnings found while developing #48.

• Pass exception through to LogError().
• Add calls to `ConfigureAwait(false).
• Add missing XML documentation.
• Suppress CA1032 on SSMParameterToLongException (sic).
• Suppress CA1031.
• Remove redundant assignment and namespace.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[normj]

Thanks for the cleanup effort @martincostello