RestartManager path containing double slash

Hey we've noticed that if we provide a path containing two forward slashes beside each other the following error occurs

```
P=0000000:Program abort called in file ``/path/to/samrai/source/SAMRAI/tbox/Utilities.cpp'' at line 118
P=0000000:ERROR MESSAGE:
P=0000000:Error in Utilities::recursiveMkdir...
P=0000000: Cannot create directory = path/to/restarts/
P=0000000:
```

We've wrapped this on our end to not let this happen but maybe you want to handle it too

Start in SAMRAI/tbox/Utilities.cpp at Utilities::recursiveMkdir and trace how RestartManager passes paths containing adjacent slashes. Reproduce the failure with a restart path containing a double slash, then inspect nearby tests or directory-creation callers. Done means the path is handled successfully without breaking normal restart-directory creation.

Written by the indexing model from the issue text.