Acquire a lease on the blob before rebooting the device.

Earlier, we were rebooting the device immediately after
committing the blob. Technically, there are no guarantees
whether or not the blob will be available for the app
after the reboot unless there was a lease on the blob.

Bug: 208517558
Test: atest --test-mapping apex/blobstore
Change-Id: I770fad95e1866f58b4b42b22243f263edf65c217
2 files changed