Fix handling of duplicate matches on id expansion

Fixes: containers#12963

[NO NEW TESTS NEEDED] I don't know how to create two
containers with the same first digit of the digest,
which I could them attempt to remove.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

pkg/api/handlers/utils/errors.go

@@ -40,10 +40,12 @@ func VolumeNotFound(w http.ResponseWriter, name string, err error) {
 }
 
 func ContainerNotFound(w http.ResponseWriter, name string, err error) {
-	if errors.Cause(err) != define.ErrNoSuchCtr {
+	switch errors.Cause(err) {
+	case define.ErrNoSuchCtr, define.ErrCtrExists:
+		Error(w, http.StatusNotFound, err)
+	default:
 		InternalServerError(w, err)
 	}
-	Error(w, http.StatusNotFound, err)
 }
 
 func ImageNotFound(w http.ResponseWriter, name string, err error) {