find out what MAPL does to initialize LANDPERT if restart is specified but not provided

[gmao-rreichle]

@gmao-qliu reports that she was able to specify a LANDPERT restart file in LDAS.rc for the first segment of a run although an ensemble of such files does not exist initially.
This probably works because the LANDPERT internal_specs (restart variables) are not "restart_required" and can be cold-started.
The question is what MAPL does to initialize LANDPERT if there is no restart file.
The desired behavior would (probably) be to set the first element of the seed vector to 0, which is perhaps the default behavior for MAPL cold starts. But that is not clear and may also depend on the compiler choice.
If we can get a "good" cold-start of LANDPERT with the specification of (initially) non-existent files, then we should just have ldas_setup always add the LANDPERT_INTERNAL_RESTART_FILE into LDAS.rc, regardless of whether the file exists. Assuming this work, we can remove the editing of LDAS.rc as part of the lenkf.j post-processing, which was introduced as a quick fix on 11 Jun 2020.

[gmao-rreichle]

@gmao-qliu reminded me that this fix didn't make it into the beta.7 tag, and consequently also isn't in the beta.8 tag.
Given the potential for getting the run config wrong for ensemble runs that are restarted from a single member, this issue should be addressed sooner rather than later.

cc: @saraqzhang @weiyuan-jiang

[gmao-rreichle]

addressed with #276