Different behaviour between engines in xarray.Dataset.to_netcdf

What happened:
Depending on the engine used writing a xarray.Dataset the behaviour can change notably using engine='scipy' will overwrite the file even if another file is using it. I am not sure this is a pure `xarray problem but would nice to be consistent ....

What you expected to happen:
All engines throw an error if the file is being used

Minimal Complete Verifiable Example:
Open 1 terminal and run:

import fasteners

lock = fasteners.InterProcessLock('test.nc') 
lock.acquire()

This is just to create a locked file, you can do this in another manner.

This is the bug:

import xarray as xr

da = xr.DataArray(
    [1, 2, 3, 4],
    dims=['lat'],
    name='lat'
)
ds = da.to_dataset()

ds.to_netcdf('test.nc', engine='netcdf4')
-> PermissionError: [Errno 13] Permission denied: b'/XXXX/XXX/bug.nc'

ds.to_netcdf('.nc', engine='h5netcdf')
-> OSError: Unable to create file (unable to lock file, errno = 35, error message = 'Resource temporarily unavailable')

ds.to_netcdf('.nc', engine='scipy')
-> no output (Saves file with no problems??)

Anything else we need to know?:

Environment:

Start at xarray.Dataset.to_netcdf and reproduce the reported behavior with the netcdf4, h5netcdf, and scipy engines using the provided locked-file example. Trace the engine-specific write paths and identify where regression coverage belongs. Done means the intended behavior for a locked output file is consistent across the affected engines and is covered by tests.