set default value for instance_name
align arguments
rewrite tests' configs collection
get rid of unused instance variables
rewrite collect_instances_params
shorten invocation chains
remove redundant key access
add tests' configs dir parameter
Merge branch 'refactoring/runtests' of https://github.com/itIGO/elliptics-qa into itIGO-refactoring/runtests
Merge branch 'itIGO-refactoring/runtests' into develop