testconf: improve error handling

Signed-off-by: Petar Koretic <petar.koretic@sartura.hr>
server: tests: add opencpe firmware-job test

Signed-off-by: Petar Koretic <petar.koretic@sartura.hr>
server: add authenetication retry option

Default option was to return error on first failed try. This commit
makes this customizable so one can allow client to try different methods
multiple times. Default retry value is 3.

Signed-off-by: Petar Koretic <petar.koretic@sartura.hr>
testconf: generate default test name dynamically

Default value for the test was 'unknown' if not set. Replace that with
dynamically generated name from calling script. One can still set name
manually when desired.

Signed-off-by: Petar Koretic <petar.koretic@sartura.hr>