Subscription updater: don't turn data off if we've never set a deafult

In the case of an MSIM device that has only had 1 SIM and then you swap
the sim to another slot, the data will turn off, but it's the same SIM
and should not.

Change-Id: I77ed8c22663aa10d211e6f4de06b791c1a8f0971
Signed-off-by: Roman Birg <roman@cyngn.com>