Decode error
Decode error

When attempting invoke setup trust, if the passed in cert fails to
decode there isn't any error to return and will just return nil.

Considering this will always be nil, then the error message will never
be displayed. Change to always return the error and will work as
expected.

Signed-off-by: ca79d94dd6bfa8eed56dd1bcbd12f2c69d8c7afa@canonical.com

mjeanson/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,hallyn/lxd,Skarlso/lxd,Skarlso/lxd,hallyn/lxd,Skarlso/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,atxwebs/lxd,lxc/lxd,Skarlso/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,mjeanson/lxd,mjeanson/lxd