[autotest] return set_power_state return value in wrapper class

The return value is used to determine if a set_power_state call is successful.

BUG=chromium:243567
TEST=change local rpm config to use dshi.mtv as frontend_addr
According to bug 364323, SSH_LOGIN_CMD may need to append: -c aes128-cbc
update shadow config in CROS with:
rpm_frontend_uri: http://dshi.mtv.corp.google.com:9999
run:  ./rpm_client.py -m chromeos3-row2-rack2-host1 -s OFF
confirm rpm controller status in chromeos3-row2-rack2-rpm1.cros.corp.google.com

Change-Id: I433814cdbd403b3f586f3ab31e9e51ad7211b94a
Reviewed-on: https://chromium-review.googlesource.com/198929
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
1 file changed