Dropdowns always open if any parent has .open

Created by: mattdwen

With 2.0.3, the dropdowns.less at line 101 file specifies:

.open {
// IE7's z-index only goes to the nearest positioned ancestor, which would
// make the menu appear below buttons that appeared later on the page
*z-index: @zindexDropdown;

.dropdown-menu {
display: block;
}
}

Which makes any dropdown with a parent .open, open as default.

Changing 106 to:

> .dropdown-menu {

forces it so only direct child drop-downs are open.