- new SENDMAIL function that mirrors the perl lib's
- retry logic for communicating with the dslice agent when a slice/sliver is
  being deleted (plabnode free)

One thing I'd like to do is write a wrapper class around agent and node
manager communication since it can be flaky - would clean up a and simplify
things.  Maybe just wait since we're going to have to port over to dynamic
slices soon enough.