SQL Perf Counter fixes

Duplicate backup devices (that we don't display), HADR seeding tests and
a bad counter ref after a recent pull request #18 all fixed up
Retry attempts for Active Directory security provider

When an app restart happens the COM underpinnings of
System.DirectoryServices can ref the old app domain causing all sorts of
run.  Sticking logic for 3 retries on Active Directory fetches.