Changing aer_simulator_statevector checking method

[doichanj]

Summary

Changed comparison of backend name by using == to in if the backend is aer_simulator_statevector or not.

Details and comments

Because GPU simulator's backend name is aer_simulator_statevector_gpu using == returns False.
And some of the functionality of statevector simulator was not called correctly for GPU backend.

So by checking
if "aer_simulator_statevector" in backend.name():
returns True both for CPU and GPU simulator.

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[coveralls]

Pull Request Test Coverage Report for Build 2800626840

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 84.037%

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Totals
Change from base Build 2800102724:	0.003%
Covered Lines:	56089
Relevant Lines:	66743

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💛 - Coveralls

[woodsp-ibm]

Thanks for the fix. It looks good to but I think it needs a release note that describes the fix. See adding-a-new-release-note section of the contributing guide here if you need info on how to do that.

[woodsp-ibm]

Thanks for adding the release note. Looks good to me now.