bug: fix annotation bug (#1887)

#### What type of PR is this?

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/kind bug
/kind cleanup
/kind documentation
/kind feature
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#### What this PR does / why we need it:

When supplying a label in the compose file, it should stay in the output
too.

#### Which issue(s) this PR fixes:
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*Automatically closes linked issue when PR is merged.
Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
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Fixes https://github.com/kubernetes/kompose/issues/1885

#### Special notes for your reviewer:

Signed-off-by: Charlie Drage <charlie@charliedrage.com>

pkg/transformer/utils.go

@@ -249,10 +249,6 @@ func ConfigAllLabels(name string, service *kobject.ServiceConfig) map[string]str
 func ConfigAnnotations(service kobject.ServiceConfig) map[string]string {
 	annotations := map[string]string{}
 
-	if !service.WithKomposeAnnotation {
-		return annotations
-	}
-
 	for key, value := range service.Annotations {
 		annotations[key] = value
 	}
@@ -270,6 +266,15 @@ func ConfigAnnotations(service kobject.ServiceConfig) map[string]string {
 		annotations["kompose.version"] = version.VERSION + " (" + version.GITCOMMIT + ")"
 	}
 
+	// if service.WithKomposeAnnotation = false, we remove **all** kompose annotations (io.kompose.*)
+	if !service.WithKomposeAnnotation {
+		for key := range annotations {
+			if strings.HasPrefix(key, "kompose.") {
+				delete(annotations, key)
+			}
+		}
+	}
+
 	return annotations
 }