Replaces use of vdu_name for vdu_id and vdu_count_index in VCACollector

vdu_name param is no longer configured by LCM, causing issues during
collection of VCA metrics. To fix that, it has been replaced by currently
configured params: vdu_id and vdu_count_index, which are obtained from the
vdur.

Fixes bug 762

Change-Id: Ic8cc7e8572bfc6d78493fdceea32375c6f3a379e
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>