Move dumpstate to calling getprop.

There's no obvious reason for reinventing the wheel like this (given that
dumpstate already spends most of its time calling out to other utilities),
and I keep having to come and fix this code.

(This time the problem being that there's no longer a limit on system
property names.)

Bug: http://b/33926793
Test: ran dumpstate
Change-Id: I08281680df5aabfdb39228abf8c2aab089cc8b9e