set clobber variable from run configuration file

[junwang-noaa]

In the UFS coupled test, any existing GOCART history files need to be removed before the model starts. We hope to have a configuration variable to control if model can overwrite an existing GOCART history file.

[junwang-noaa]

@weiyuan-jiang FYI.

[mathomp4]

@junwang-noaa History does currently have a global variable to do this:

Allow_Overwrite: .true.

will allow history to clobber.

You put this at the top much like CONTACT:, etc.

[bbakernoaa]

@mathomp4 We just remembered this a little bit ago and we are testing now.

[weiyuan-jiang]

@bbakernoaa Please let me know if it works or not.

[junwang-noaa]

@weiyuan-jiang I tested in a UFS coupled test, it is working now. Thank you all!