Fix bug 659: Don't use static member variables

This fixes bug 659, where static member variables were used by the
VCAMonitor, causing unexpected behaviour when deploying and destroying a
network service multiple times.

Change-Id: Icc5e4da62aeb11e4c89ba3cf5f148c6959acf7e3
Signed-off-by: Adam Israel <adam.israel@canonical.com>