[JENKINS-18368] added isUnix override to launcher decorator classes so that isUnix is maintained for remote launcherswq

(cherry picked from commit 656738c020881e96e21511670a2dd4a6e8dad2ce)
[FIXED JENKINS-18368]: modified testcase asserts

(cherry picked from commit d6ccf84eb451517c82fe6448fe0259c5a5c112f2)
[FIXED JENKINS-18368]: added Bug attributes

(cherry picked from commit 7f67499141f325dff9fe1ea06331b2bcc0d03003)
[FIXED JENKINS-18654] exlude disabled plugins from transitive dependency list

(cherry picked from commit a6926e1c51c0650a48dec68cbe402248742dd55c)
[JENKINS-18654] testcase as suggested by kutzi

(cherry picked from commit 1f761085e20ee2aa106a196d0148e616138e31fe)
[JENKINS-18654] document unit test

(cherry picked from commit bd87d70b3aa6cd8d13dbeae56b3c09fc425e2442)