sktm retries Jenkins operations on logical errors

[spbnick]

sktm retries Jenkins operations even if the error is not transient, but logical. E.g.:

[39146] 2018-08-29 11:39:03,157  WARNING   catch <class 'jenkinsapi.custom_exceptions.UnknownJob'>: 'upstream'
[39146] 2018-08-29 11:39:03,157     INFO   now sleep 60s and try again

Consider differentiating the detected errors and aborting on logical ones.

[veruu]

@idorax , do you think you can figure out how to differentiate between the various errors?