init: Detach daemon only after sepolicy is loaded

The new sequence of operation would be:

1: Load sepolicy - Daemon will continue to be alive and serve any I/O request

2: After sepolicy loading is complete - Switch the device-mapper tables.

3: Kill the block device daemon launched in the first-stage init.

4: Re-launch the daemon with the correct selinux labels set.

5: Enforce the sepolicy

Bug: 240321741
Test: Full OTA on pixel
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Idd392f0f0aae7d93e546c0ec0762e6c07b6263e4