trusty_apploader: log to stderr

Print an error message to stderr on connection failure, so that the
command doesn't exit silently in case of the common user error of
forgetting to run it as root.

Bug: None
Test: Run as regular user, see "permission denied" message.
Change-Id: Ia213dedccab27e6152b5eb969fbee06d82d3d4ff
1 file changed