map2cam running out of file descriptors

[scsides]

ISIS version(s) affected: 4.0.1 and most likely nearly any recent version

Description
map2cam run in batch mode with 2000 images in the batch file fails around file 1018:

map2cam from= themosmap/mc02_diacria_dir_final.cub to=themosmap/$1_mapIR match=$1 -batch=cub.lis -onerror=continue -errli=mapthem.err

LOTS OF NOT SHOWN LINES WHERE map2cam WAS SUCCEEDING

---

map2cam from=themosmap/mc02_diacria_dir_final.cub to=themosmap/H0682_0003_SR2.IMG.cub_mapIR match=H0682_0003_SR2.IMG.cub
I/O ERROR Unable to open [H0682_0003_SR2.IMG.cub].
map2cam from=themosmap/mc02_diacria_dir_final.cub to=themosmap/H0682_0004_SR2.IMG.cub_mapIR match=H0682_0004_SR2.IMG.cub
terminate called after throwing an instance of 'Isis::IException'
what(): I/O ERROR Unable to open [/scratch/repos/hrsc-ssides/build/appdata/templates/labels/CubeFormatTemplate.pft].
Aborted (core dumped)

It looks like map2cam is not closing a file inside the batch loop.

ulimit -n shows an open file limit of 1024.

Running lsof while the batch is running shows that all the MATCH files remain open until the crash.

How to reproduce
See description

Possible Solution
Close the MATCH file when the ISIS main returns

Additional context

[jessemapel]

I'm curious if this exist prior to #3757. The match cube is a global variable but it should get closed during the endProcess call.

[scsides]

PR to fix has been merged