tests/test-diff-newlines.t

commands: execute checkunfinished and bailifchanged inside wlock scope

Before this patch, "hg import" executes below before acquisition of
wlock:

  - cmdutil.checkunfinished()
  - cmdutil.bailifchanged()

It may cause unintentional result, if another command runs parallelly
(see also issue4368).

To avoid this issue, this patch executes 'cmdutil.checkunfinished()'
and 'cmdutil.bailifchanged()' inside wlock scope of "hg import".

  $ hg init

  $ $PYTHON -c 'file("a", "wb").write("confuse str.splitlines\nembedded\rnewline\n")'
  $ hg ci -Ama -d '1 0'
  adding a

  $ echo clean diff >> a
  $ hg ci -mb -d '2 0'

  $ hg diff -r0 -r1
  diff -r 107ba6f817b5 -r 310ce7989cdc a
  --- a/a	Thu Jan 01 00:00:01 1970 +0000
  +++ b/a	Thu Jan 01 00:00:02 1970 +0000
  @@ -1,2 +1,3 @@
   confuse str.splitlines
   embedded\r (no-eol) (esc)
  newline
  +clean diff