Using dict.get methods to get machine.local_root

[dingzhaohan]

If local_root isn't ./, dpgen will raise error and exit, it seems local_root must be './', so I try to get a default value if machine.json doesn't provided it.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (e86d821) 47.79% compared to head (cf6ea45) 47.79%.

Additional details and impacted files

@@           Coverage Diff           @@
##            devel    #1287   +/-   ##
=======================================
  Coverage   47.79%   47.79%           
=======================================
  Files          82       82           
  Lines       14586    14586           
=======================================
  Hits         6972     6972           
  Misses       7614     7614           

Files Changed	Coverage Δ
dpgen/dispatcher/Dispatcher.py	83.78% <100.00%> (ø)

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[wanghan-iapcm]

The dispatcher module is not maintained any more. One is supposed to use https://github.com/deepmodeling/dpdispatcher.
@njzjz shall we remove dpgen/dpdispatcher?

[dingzhaohan]

func make_submission(dpgen/dispatcher/Dispatcher.py) is called in dpgen/generator/run.py. In make_submission, it first checks local_root, then initialize dpdispatcher.

[njzjz]

The dispatcher module is not maintained any more. One is supposed to use https://github.com/deepmodeling/dpdispatcher.

@njzjz shall we remove dpgen/dpdispatcher?

It now only contains a wrapper of dpdispatcher.