Zoltan2: Fixed a bug in the RCM implementation. When a diagonal matrix
was passed in and the graph had only self edges, these edges might be
all removed by the Zoltan2 graph model class. Running RCM on this graph
would cause the null array of offsets to be accessed, causing a seg
fault. More error checking is definitely needed, but I fixed this particular
case for now by checking to see if there are any edges present in the
input graph before attempting to reorder it.

I also changed a few lines that accessed raw pointers to ArrayRCPs to
instead use the operator[] of ArrayRCP.

I was developing more improvements to this algorithm a few weeks back so
this will be revisted.

Build/Test Cases Summary
Enabled Packages: Zoltan2
Enabled all Forward Packages
0) MPI_DEBUG => Skipped configure, build, test due to no enabled packages! => Does not affect push readiness! (-1.00 min)
1) SERIAL_RELEASE => Skipped configure, build, test due to no enabled packages! => Does not affect push readiness! (-1.00 min)
2) INTEL_DEBUG => passed: passed=51,notpassed=0 (7.91 min)
MueLu: simplified scalingTest xml
MueLu: fixed output problems in couple places
Added code to issue warning if any solver other than NonGradient is used with MaxTemplate.