ALLJOYN-577: Updated comment and test to use correct values

The test should have said the AllJoyn array size limit was 2^17
the test should also use the same size limit.

Change-Id: I52b0a0780a61015b902ba467084e988c3c831127
ALLJOYN-394: Fix documentation and unit test for
ProxyBusObject::GetChild.

GetChild will take the relative or absolute path which is the same as
RemoveChild.

Change-Id: Ia4527489c08d80d7d5e6be0a823839e668aaa63b