Move dumpstate to calling getprop.

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