Case postrun fails when there is a single component (is_comp_standalone == TRUE) for multi-instance cases

This started in:

https://github.com/ESCOMP/CDEPS/issues/426

where I ran a single component case with DGLC with two instances. It marks the case as failing because it doesn't find a single instance glc.log file as they are split into glc_0001.log and glc_0002.log.

The fail looks like this:

```
ERROR: Model did not complete, no /glade/derecho/scratch/erik/cases/SMS_C2_D_Lh12.f10_f10_mg37.2000_SATM_SLND_SICE_SOCN_SROF_DGLC%NOEVOLVE_SWAV.derecho_intel.clm-pauseResume.GC.ctsm545delist/run/glc.log.7026886.desched1.260805-205554 log file
```

Start with the Case postrun logic that searches for the component log after a multi-instance standalone case runs. Reproduce the DGLC scenario described in the issue and compare the expected single glc.log lookup with glc_0001.log and glc_0002.log. Done means the case is not incorrectly marked failed when the component logs are split by instance.

Written by the indexing model from the issue text.