Move 'path' package usage to 'path/filepath'.

[kkmsft]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind api-change

/kind bug

/kind cleanup
/kind deprecation
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

In case of windows, the path package functions such as 'Dir' returns faulty directory path.
For eg: 'path.Dir' on 'c:\var\lib\kubelet\pods' returns '.', where as the result should
have been 'c:\var\lib\kubelet'. The filepath package returns the right values.

> cat .\path.go

package main 
import(
        "fmt"
        "path"
        filepath "path/filepath"
)

func main() {
       p := "c:\\var\\lib\\kubelet\\pods"
       dir := path.Dir(p)
       dir1 := filepath.Dir(p)
       fmt.Printf("Just path: %s\n", dir)
       fmt.Printf("File path: %s\n", dir1)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
}                                                  

> .\path.exe 

Just path: .
File path: c:\var\lib\kubelet

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[kkmsft]

/cc @ddebroy @jingxu97 @PatrickLang

[kkmsft]

/retest

[kkmsft]

/retest

[kkmsft]

/retest

[kkmsft]

/retest

[kkmsft]

/cc @andyzhangx

[andyzhangx]

/lgtm
/priority important-soon
/sig windows

'path/filepath' supports windows.

[jsafrane]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jsafrane, kkmsft

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[kkmsft]

/kind bug

[fejta-bot]

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