Fix the implicit bug

[jijn]

• Please check if the PR fulfills these requirements

• The PR follows our guidelines (formatting & style)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Bug fix Implicit Time Dependent Fields not updated every other time step #727

• What is the current behavior? (You can also link to an open issue here)
  fields not updated every other time step

• What is the new behavior (if this is a feature change)?
  they are updated correctly now.
  For implicit, get_value(old1) should point to the solved solution of the previous step.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No
  I updated gold_output.txt for allen_cahn_implicit

• Other information:
  We need to wait for @fractalsbyx for the best solution.

[fractalsbyx]

Could you investigate why these break?