Do not use spawn_resources, use new simpler script

this is temporary solution, till the spawn_resources thing starts working fine.
Fix issues caused by Jenkins permalinks not behaving as promised in the docs
Handle cases where stage version or new version is not specified/available.
Update upgrade job to test upgrade in virtual machines now
Merge branch 'master' of https://github.com/rushiagr/pipeline

Conflicts:
	jenkins-jobs/run_upgrade.sh
Destroy environment after running tests, for upgrade job
Properly handle parameter for the non-functional test job.
Fix bug where NFT stage needs to create artifact even when there is nothing to test.
Fix issues with correctly handling the last tested version for upgrade stage.
Fix issues with correctly handling the last tested version for staging stage.
Fix typo in artifact file name.
Fix issues with artifact names
Updated README to reflect plugin we are using.
Fix config problem where upgrade job was not automatically triggering staging job
Fix an issue with publishing artifacts
Fix a few corner cases in the pipeline shell scripts.
Fixed a bug where upgrade would run unnecessarily
Update sources.list to not point to port 81 but normal HTTP port 80
Fix doc for repo mirror URL

The doc was outdated, pointing to old URL (port 81) which dont work now.
Update readme to provide details about snapshots repository

Fix #4.