init: verify size of property buffers passed to property_get

Verify that the buffer passed as the value parameter to property_get
is always big enough.

(cherry picked from commit 88ac54a4e8d2a63e4fd9c465e115795ace316776)

Change-Id: Iacc2b42bfe4069e0bfcbb1c48474f30126a93139
init: fix copying boot properties

The previous patch "init: verify size of property buffers passed
to property_get" incorrectly modified one of the callers,
resulting in ro.serialno, ro.bootmode, ro.baseband, and
ro.bootloader always being set to their default values.

Bug: 9469860

(cherry picked from commit 67e3663fc93c65b69b5d121db05b0833b98d97f1)

Change-Id: Ia7b337e1fab6e334729f47ee1269e6c736615177