Bugfix for sparse communication

[lroberts36]

PR Summary

If a variable was deallocated at the end of one step and reallocated during the next call to ReceiveBoundBufs, it would appear to SetBounds that the BndInfo cache was not stale (since the field was allocated on subsequent calls to SetBounds) even though the variable itself contained newly allocated memory. This is fixed by checking the value of Variable::GetAllocationStatus() in CheckSendBufferCacheForRebuild andCheckReceiveBufferCacheForRebuild against the value that is now store in BndInfo. GetAllocationStatus() returns zero if the variable is deallocated and the number of times the variable has been allocated over the simulation otherwise.

This should not have any impact on codes that do not use sparse variables.

PR Checklist

• Code passes cpplint
• Code is formatted
• Changes are summarized in CHANGELOG.md
• CI has been triggered on Darwin for performance regression tests.
• (@lanl.gov employees) Update copyright on changed files

[jdolence]

LGTM. Thanks for the fix!

[pdmullen]

LGTM