Describe the bug
When trying to convert Scene containing data read with the seviri_l1b_nc reader merging fails. The reason is the acq_time coordinate. The option compat="override" (which picks the variable from the first dataset) solves the problem.
Another possible solution would be to drop the variable.

To Reproduce

fn = [seviri netcdf files]
msgscn = Scene(reader="seviri_l1b_nc", filenames=fn)
msgscn.load(["IR_108", "VIS006"])
msgscn.to_xarray_dataset()

Expected behavior
A xarray.Dataset should be returned.

Actual results
MergeError: conflicting values for variable 'acq_time' on objects to be combined. You can skip this check by specifying compat='override'.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment Info:

• OS: Linux
• Satpy Version: 0.36.1
• PyResample Version: 1.19.0