[FIXED JENKINS-19506] - Prevent errors on nested wrappers usage
The provides workarounds for NPEs in Launcher::envs() and also properly calls inner launcher wrappers.
Resolves https://issues.jenkins-ci.org/browse/JENKINS-19506

Signed-off-by: Oleg Nenashev <nenashev@synopsys.com>
Merge pull request #11 from synopsys-arc-oss/nested_wrappers_fix

[FIXED JENKINS-19506] - Prevent errors on nested wrappers usage