#1429 Contour annotations do not always turn off

[Scott]

The contour labels don't get disabled when turning a contour instance off.

To reproduce:
1) Load the session file /glade/p/VAST/VAPOR/{this bug #}/FinalSession.vdf
2) Import any WRF file into current session from /glade/p/VAST/VAPOR/Data/WRF/Katrina
3) Enable the contour renderer, then disable it. The annotations will persist no matter what.