In isMobileOk don't execute finally if mobile data is not supported.

Move the early return outside the try {} finally so we don't call
setEnableFailFastMobileData(DctContants.DISABLED). Otherwise
referencing counting is wrong and an exception is thrown in DcTrackerBase.

Bug: 10304904
Change-Id: I5ba5121e473bada9f3daa8d6f3d3577cec8212fc