Add json key file support for acloud.

Also add an option to let acloud accept json key file path option.

Bug: 111601636
Test: unit test and manually
Change-Id: Idcdcd533018462d648229ae2c6e9d5b9626821b9
Merged-In: Ie5834e683634f82d6e84a76e027adfa91913c59a
10 files changed