Add regression tests for SMB registry configuration

PR: https://github.com/freenas/freenas/pull/5297

• Validate that add, rename, delete are performed correctly when
  multiple shares are present.
• Validate that SMB share presets are correctly applied to server
  running configuration on update.
• Validate that SMB auxiliary parameters are correctly applied
  on create and update.
  • • Comments are preserved.
    • user-defined aux params are applied over presets
• Rename "level 2 oplocks" to "level2 oplocks" for consistency with
  normalization that occurs in libsmbconf