Errors returned by the system are improperly wrapped.

[Nashwan Azhari]

In most places where calls are done to the system the errors are wrapped into the corresponding error type before being sent upwards. There are some, however, in which the error is wrapped in the generic Err type that can be found in the /errors package.

The places where such issues surface in the tests are the following:

apiserver/debuglog_test.go: 61
cmd/juju/publish_test.go: 98
cmd/juju/set_test.go: 101, 114
cmd/jujud/run_test.go: 202
provider/azure/config_test: 184
provider/joyent/config_test:371
worker/uniter/runner/jujuc/tools_test.go: 81
worker/upgrader/upgrader_test.go: 286

For now, the platform-independence of these particular tests is being assured by this PR: https://github.com/juju/juju/pull/1237 , however, the sources of these errors must be traced and proper wrapping with errors.NewNotFound() must be done for them.