bootstat: local GetProperty use libbase

libbase GetProperty collects the properties properly, which also
allow for content greater than 128 bytes in length.

Replace internal GetProperty and SetProperty helpers with libbase
version.

Test: unit tests
Bug: 121161069
Bug: 124114707
Change-Id: Ic0829955705ebaa19d747bb3f6942f4b9786316a
1 file changed