CA-78558: Fix marking of VIFs as disconnected.

Previously the disconnect flag as determined by the VIF's locking mode
overwrote the disconnect flag as determined by the VIF's carrier field.

After this patch, the disconnect flag is set if the VIF's carrier field
is false, OR if the the VIF is disabled.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1078 from robhoes/carrier

TALLAHASSEE: CA-78558: Fix marking of VIFs as disconnected.