Fixed error in the get members and get properties functions

alljoyn_interfacedescription_getmembers and
alljoyn_interfacedescription_getproperties would return zero as the total
number of members or properties when a NULL pointer was passed in as the
array pointer.  The functions should return the number of members or
properties in the InterfaceDescription.

Added code to the unit test to verify that the right values are returned.

Change-Id: I42e2e7bf8d4c2967ea7c482738cf9b072a291f82