Tell installd when boot completes.

installd can then clear the ".booting" marker from the dalvik-cache
(owned by root). This marker is used to detect boot loops.

bug: 18280671

(cherry picked from commit 76a748e62f354c799342044f724e1f4b80121837)

Change-Id: I2364c05837ac04d428b5a34ab1802964a11d2df4