fold: when folding drafts, make result draft even if phases.new-commit=secret

Since hg 4.7, there has been a `fixphase` argument to
`scmutil.cleanupnodes()`. This patch makes it so we use that for `hg
fold` if it's available. I'll leave it for later to pass it for all
the other commands.
8 jobs for topic/default/fold-phases in 4 minutes and 27 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #119948
checks-py2

00:02:35

passed #119949
checks-py3

00:01:01

passed #119954
doc

00:00:33

manual #119947
allowed to fail manual
pytype
failed #119950
tests-py2-cext

00:04:27

failed #119951
tests-py2-pure

00:03:32

failed #119952
tests-py3-cext

00:02:26

failed #119953
tests-py3-pure

00:03:36

 
Name Stage Failure
failed
tests-py2-cext Test
Failed test-topic-stack.t: output changed
Failed test-topic-tutorial.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 194 tests, 6 skipped, 73 failed.
python hash seed: 4253469480
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1
failed
tests-py3-pure Test
Failed test-topic-stack.t: output changed
Failed test-topic-tutorial.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 194 tests, 6 skipped, 73 failed.
python hash seed: 2357776597
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1
failed
tests-py2-pure Test
Failed test-topic-stack.t: output changed
Failed test-topic-tutorial.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 194 tests, 6 skipped, 73 failed.
python hash seed: 1944164460
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1
failed
tests-py3-cext Test
Failed test-topic-stack.t: output changed
Failed test-topic-tutorial.t: output changed
Failed test-topic.t: output changed
Failed test-unstability-resolution-result.t: output changed
# Ran 194 tests, 6 skipped, 73 failed.
python hash seed: 2264967451
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1