v_astra in MWM_ASTRA paths

For DR20, we have reverted back to the older use of v_astra in the tree structure for MWM_ASTRA related paths. For example, in IPL-4 we changed to: https://github.com/sdss/tree/blob/fc4569880c9c2e5f1c48f78423c54d2fee645f8f/data/ipl4.cfg#L194

Now in DR20, we have reverted to using the full version of astra in the file name and including it in the higher level directory. An example of the path for the same summary file in DR20 is:

/uufs/chpc.utah.edu/common/home/sdss52/dr20/spectro/astra/0.8.1/summary/mwmAllStar-0.8.1.fits.gz

So, in tree should be:

mwmAllStar = $MWM_ASTRA/{v_astra}/summary/mwmAllStar-{v_astra}.fits

This is the same as it was in DR19 and IPL-3.

So, the dr20.cfg file should reflect this.

Additionally, we are currently rerunning IPL-4. I think the plan is to have the same tree structure as DR20 (@andycasey needs to confirm this though). If so, we need to also change the ipl4.cfg file to reflect this change.