Fix issue where crosperf can't find local cros_scratch.

Crosperf was assuming the user always has an NFS home directory,
and was looking for the cros_scratch directory there.  This makes
crosperf use the user's home directory, whether it's NFS or local.

Also change --share_users, which also assumed NFS home directories,
to --share_cache, which requires specification of the cache path(s)
to use.

BUG=None
TEST=Tested this with my new local homedir.

Change-Id: I28d15467dfbd25b8b237cefa2979d3fd9464a7a7
Reviewed-on: https://chrome-internal-review.googlesource.com/179978
Reviewed-by: Yunlian Jiang <yunlian@google.com>
Commit-Queue: Caroline Tice <cmtice@google.com>
Tested-by: Caroline Tice <cmtice@google.com>
8 files changed