Asan_extract: Add FDE check

Under full-disk encryption, we must skip extracting libraries
into the temporary /data directory. It is too small, and the
framework will not be able to come up.

Add a check for the vold.decrypt system property. As it turns
out that we can't reliably use this, also add a size check
(and use 512M = 131072 4K blocks as the limit).

Bug: 36458146
Test: m && m SANITIZE_TARGET=address SANITIZE_TARGET_SYSTEM=true
Change-Id: Ib350094b049b6e75832d393527b8b62a58a7fece