Fix remaining file related CTS Test failures.

Most failures were because tests were trying to
open files relative to the current working directory,
instead of in a temp directory.

FileTest was failing because it didn't construct
paths correctly. It would add an additional separator
char even if the path already ended with one.

Change-Id: Ie90aed84f81275924558e9dba43d71748dbb4076
10 files changed