unittests: Fixes unit tests for Windows

Currently, there are some unit tests that are failing on Windows due to
various reasons:

- config options not supported on Windows.
- files not closed, which means that they cannot be removed / renamed.
- paths not properly joined (filepath.Join should be used).
- time.Now() is not as precise on Windows, which means that 2
  consecutive calls may return the same timestamp.
- different error messages on Windows.
- files have \r\n line endings on Windows.
- /tmp directory being used, which might not exist on Windows. Instead,
  the OS-specific Temp directory should be used.
- the default value for Kubelet's EvictionHard field was containing
  OS-specific fields. This is now moved, the field is now set during
  Kubelet's initialization, after the config file is read.

pkg/kubelet/apis/config/validation/validation_test.go

@@ -34,8 +34,8 @@ import (
 
 var (
 	successConfig = kubeletconfig.KubeletConfiguration{
-		CgroupsPerQOS:                   true,
-		EnforceNodeAllocatable:          []string{"pods", "system-reserved", "kube-reserved"},
+		CgroupsPerQOS:                   cgroupsPerQOS,
+		EnforceNodeAllocatable:          enforceNodeAllocatable,
 		SystemReservedCgroup:            "/system.slice",
 		KubeReservedCgroup:              "/kubelet.service",
 		SystemCgroups:                   "",