Fix for multiple status-set - related to bug 1588462

This change fixes the obvious race for a status_set() between
check_optional_interfaces() and assess_status() as the later calls the former
which calls status_set(), returns the status, which is then potentially set
again by the assess_status() function.  This cleans up the code so that only a
single status_set() is performed when calling assess_status().

Change-Id: I928f60967e4a7588df2b25136525391c283cda14
Related-Bug:#1588462