disable plugin2 in 6u10, plugin2 is enable after 7u4 installed.

Tested configs: Win7-x86, UAC On
Tested senarios: Intall 6u10 + Select Plugin1+ install 7u4

Steps to reproduce:
1) Install 6u10
2) Disable "JCP->Advanced->Java Plug-in->Enable the next generation Java Plug-in"
3) install 7u4
Actual Result:
- "JCP->Advanced->Java Plug-in->Enable the next generation Java Plug-in" is enable after 7u4 installed.
Expected Result: Plug-in 1 is the default plugin