e2e(vm_sidebar): create e2e test for vm_sidebar storage tab (#1260)

[coveralls]

Pull Request Test Coverage Report for Build 1811

• 17 of 25 (68.0%) changed or added relevant lines in 3 files are covered.
• 41 unchanged lines in 2 files lost coverage.
• Overall coverage remained the same at 53.439%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/app/shared/services/base-backend.service.ts	9	11	81.82%
src/app/shared/services/ssh-keypair.service.ts	1	3	33.33%
src/app/utils/encoders/custom-encoder.ts	7	11	63.64%
<!--	Total:	17	25	68.0%	-->

Files with Coverage Reduction	New Missed Lines	%
src/app/shared/services/ssh-keypair.service.ts	4	65.38%
src/app/shared/services/base-backend.service.ts	37	63.05%
<!--	Total:	41		-->

Totals
Change from base Build 1810:	0.0%
Covered Lines:	9527
Relevant Lines:	15823

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💛 - Coveralls