Resolve mo_gaal device(gpu/cpu) issue

[zhuox5]

All Submissions Basics:

• [x] Have you followed the guidelines in our Contributing document?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you checked all Issues to tie the PR to a specific one?

All Submissions Cores:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [x] Have you written new tests for your core changes, as applicable?
• [x] Have you successfully ran tests with your changes locally?
• [x] Does your submission pass tests, including CircleCI, Travis CI, and AppVeyor?
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New Model Submissions:

• [x] Have you created a .py in ~/pyod/models/?
• [x] Have you created a _example.py in ~/examples/?
• [x] Have you created a test_.py in ~/pyod/test/?
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[coveralls]

Pull Request Test Coverage Report for Build 9621576231

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.171%

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Totals
Change from base Build 9620070062:	0.0%
Covered Lines:	9370
Relevant Lines:	9950

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9621576231

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.171%

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Totals
Change from base Build 9620070062:	0.0%
Covered Lines:	9370
Relevant Lines:	9950

---

💛 - Coveralls