vma: Add !VVAR condition to vma_entry_can_be_lazy

[yota9]

Currently most of the times we don't have problems with VVAR segment and
lazy restore because when VDSO is parked there is an munmap call that
calls UFFDIO_UNREGISTER on the destination address.
But we don't want to enable userfaultfd for VDSO and VVAR at the first
place.

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (1e4f5fb) 70.54% compared to head (1c5357b) 70.54%.

❗ Current head 1c5357b differs from pull request most recent head df497f2. Consider uploading reports for the commit df497f2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##           criu-dev    #2272   +/-   ##
=========================================
  Coverage     70.54%   70.54%           
=========================================
  Files           133      132    -1     
  Lines         33522    33510   -12     
=========================================
- Hits          23647    23640    -7     
+ Misses         9875     9870    -5     

Files	Coverage Δ
criu/include/vma.h	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[avagin]

lgtm

[rppt]

AFAIU Currently most of the times we don't have problems with VVAR segment due
to during parking vdso on it's old place mremap is used and during it
munmap is called to destination address which results in calling
UFFDIO_UNREGISTER. But as for VDSO we don't want to enable uffd for these addresses at firse place.

I find the changelog a bit hard to parse, how about

Currently most of the times we don't have problems with VVAR segment and lazy restore because when VDSO is parked there is an munmap call that calls UFFDIO_UNREGISTER on the destination address.
But we don't want to enable userfaultfd for VDSO and VVAR at the first place.

Other than that, LGTM

[yota9]

@rppt Thanks, done. Please merge it since I don't have rights.