Fixed data disconnected for 10 seconds when disabling tethering

Before we always tear down the tethering data connection even
though the same data connection could be used for other
purposes (e.g. internet, mms). Now we don't do that if the
data connection can be shared for other purposes. Note that
we only do this for non-CDMA case.

Bug: 132322044
Bug: 131930219
Bug: 129387119

Test: Manual
Merged-In: I4061c4b86c09718d834a5dc16d24c52ed7801b0f
Change-Id: I4061c4b86c09718d834a5dc16d24c52ed7801b0f
(cherry picked from commit a40ce990)