only modify velocity of water during ocean wave initialization

[mbkuhn]

Summary

Necessary for ABL + waves simulations. To go with other physics classes, the ocean waves need not overwrite the velocities in the air.

Pull request type

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Checklist

The following is included:

• new unit-test(s)
• new regression test(s)
• documentation for new capability

This PR was tested by running:

• the unit tests
  • on GPU
  • on CPU
• the regression tests
  • on GPU
  • on CPU

Issue Number: maybe #1162

[marchdf]

This solves #1162 !!