Gracefully handle "needs init" transport errors at finish

Although it's typical for a backup transport to report that it
needs an explicit initialization opportunity when the backup is
initiated, it can sometimes come to pass that the "needs init"
error condition is reported at backup *finish*.  In this case the
framework side was failing to properly reset all of the relevant
state.  The end result was to spin hard forever, holding wakelocks
and continually failing to actually perform the necessary init
operation, possibly continuing even after a reboot.  Fixed.

Bug 5434579

Change-Id: If1d72c338526e4019ea524c48a11e71e44e77f71