[YUNIKORN-2051] fix staticcheck errors

[FrankYang0529]

What is this PR for?

pkg/admission/conf/am_conf.go:400:6: func parseConfigInt is unused (U1000)
pkg/admission/webhook_manager.go:72:2: field namespace is unused (U1000)
pkg/appmgmt/general/general.go:123:9: assigning the result of this type assertion to a variable (switch obj := obj.(type)) could eliminate type assertions in switch cases (S1034)
    pkg/appmgmt/general/general.go:125:10: could eliminate this type assertion
pkg/cache/context_test.go:471:2: this value of found is never used (SA4006)
pkg/cache/task_test.go:31:2: package "k8s.io/apimachinery/pkg/apis/meta/v1" is being imported more than once (ST1019)
    pkg/cache/task_test.go:32:2: other import of "k8s.io/apimachinery/pkg/apis/meta/v1"
pkg/cmd/shim/main.go:53:15: type assertion to the same type: serviceContext.RMProxy already has type api.SchedulerAPI (S1040)
pkg/dispatcher/dispatch_test.go:209:4: should use fmt.Printf instead of fmt.Println(fmt.Sprintf(...)) (but don't forget the newline) (S1038)
pkg/dispatcher/dispatch_test.go:211:4: should use fmt.Printf instead of fmt.Println(fmt.Sprintf(...)) (but don't forget the newline) (S1038)
pkg/plugin/scheduler_plugin.go:268:15: type assertion to the same type: serviceContext.RMProxy already has type api.SchedulerAPI (S1040)
test/e2e/admission_controller/admission_controller_suite_test.go:28:2: package "github.com/onsi/gomega" is being imported more than once (ST1019)
    test/e2e/admission_controller/admission_controller_suite_test.go:29:2: other import of "github.com/onsi/gomega"
test/e2e/framework/helpers/common/utils.go:203:15: error strings should not be capitalized (ST1005)
test/e2e/framework/helpers/k8s/k8s_utils.go:759:99: error should be returned as the last argument (ST1008)
test/e2e/framework/helpers/yunikorn/rest_api_utils.go:294:14: error strings should not be capitalized (ST1005)
test/e2e/node_resources/node_resources_suite_test.go:57:5: var kClient is unused (U1000)

What type of PR is it?

• - Improvement

What is the Jira issue?

https://issues.apache.org/jira/browse/YUNIKORN-2051

[codecov]

Codecov Report

Merging #693 (6c7fcec) into master (7b08702) will increase coverage by 0.07%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #693      +/-   ##
==========================================
+ Coverage   71.81%   71.89%   +0.07%     
==========================================
  Files          51       51              
  Lines        8105     8096       -9     
==========================================
  Hits         5821     5821              
+ Misses       2084     2075       -9     
  Partials      200      200              

Files	Coverage Δ
pkg/admission/conf/am_conf.go	72.10% <ø> (+2.68%)	⬆️
pkg/admission/webhook_manager.go	77.06% <ø> (ø)
pkg/appmgmt/general/general.go	65.90% <0.00%> (ø)

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[pbacsko]

+1