refactor: Satisfy linter in zonesToRegion (#2735)

* Satisfy linter in `zonesToRegion`

* Ensure consistent region ordering

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/kube/volume/volume.go

@@ -348,19 +348,16 @@ func zoneToRegion(zone string) string {
 }
 
 func zonesToRegions(zone string) []string {
-	reg := map[string]struct{}{}
-	// TODO: gocritic rule below suggests to use regexp.MustCompile but it
-	// panics if regex cannot be compiled. We should add proper test before
-	// enabling this below so that no change to this regex results in a panic
-	r, _ := regexp.Compile("-?[a-z]$") //nolint:gocritic
+	reg := map[string]bool{}
+	var regions []string
+	r := regexp.MustCompile("-?[a-z]$")
 	for _, z := range strings.Split(zone, RegionZoneSeparator) {
 		zone = r.ReplaceAllString(z, "")
-		reg[zone] = struct{}{}
+		if _, ok := reg[zone]; !ok {
+			reg[zone] = true
+			regions = append(regions, zone)
+		}
 	}
 
-	var regions []string
-	for k := range reg {
-		regions = append(regions, k)
-	}
 	return regions
 }

pkg/kube/volume/volume_test.go

@@ -203,7 +203,7 @@ func (s *TestVolSuite) fakeUnstructuredSnasphotWSize(vsName, namespace, size str
 }
 
 func (s *TestVolSuite) TestZoneToRegion(c *C) {
-	for _, tc := range []struct {
+	for idx, tc := range []struct {
 		zone           string
 		expectedRegion []string
 	}{
@@ -237,27 +237,6 @@ func (s *TestVolSuite) TestZoneToRegion(c *C) {
 		},
 	} {
 		reg := zonesToRegions(tc.zone)
-		c.Assert(slicesEqual(reg, tc.expectedRegion), Equals, true)
-	}
-}
-
-// slicesEqual compares two unordered slices and returns true if
-// both of them have same elements
-func slicesEqual(one, two []string) bool {
-	if len(one) != len(two) {
-		return false
-	}
-
-	for _, o := range one {
-		var found bool
-		for _, t := range two {
-			if o == t {
-				found = true
-			}
-		}
-		if !found {
-			return false
-		}
+		c.Assert(reg, DeepEquals, tc.expectedRegion, Commentf("Case #%d", idx))
 	}
-	return true
 }