Fix dnd-tests-open-remote-url on EMBA

* test/lisp/dnd-tests.el (dnd-tests-open-remote-url): Check for
ftp client.
10 jobs for master in 137 minutes and 11 seconds (queued for 12 seconds)
Status Job ID Name Coverage
  Build Images
passed #48039
build-image-inotify

00:41:57

 
  Normal
passed #48040
test-all-inotify

00:29:43

 
  Platform Images
passed #48041
build-image-filenotify-gio

00:41:02

passed #48042
build-image-gnustep

00:43:25

 
  Platforms
passed #48043
test-filenotify-gio

00:15:14

passed #48044
test-gnustep

00:02:13

 
  Native Comp Images
passed #48045
build-native-comp-speed0

01:43:21

failed #48046
build-native-comp-speed1

00:04:00

failed #48047
build-native-comp-speed2

00:03:12

 
  Native Comp
passed #48048
test-native-comp-speed0

00:33:45

 
Name Stage Failure
failed
build-native-comp-speed1 Native Comp Images
rpc error: code = Unavailable desc = transport is closing
Running after_script
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
find: build-native-comp-speed1-ec1fffde: No such file or directory
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
build-native-comp-speed2 Native Comp Images
 > [emacs-base 1/2] FROM docker.io/library/debian:stretch:
------
no active session for 9yyhaor8cpaxounkx5tnzi7y6: context deadline exceeded
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
find: build-native-comp-speed2-ec1fffde: No such file or directory
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
ERROR: Job failed: exit code 1