[Upgrade] Check version pre-check from before_upgrade_checker sometimes return false-positive results

[Tatyanka]

Actual Result:

Nailgun back such version(api/versoins)
{"build_id": "2014-07-24_02-01-14", "ostf_sha": "81b019a502711dfcd935a981b292e88eb956b141", "build_number": "351", "auth_required": false, "api": "1.0", "nailgun_sha": "744e17cc03207c46ecd79f4ac78fde98f75aec2f", "production": "docker", "fuelmain_sha": "103ce9abd6e2632ec1029d1aa3e918517417cba3", "astute_sha": "fd9b8e3b6f59b2727b1b037054f10e0dd7bd37f1", "feature_groups": ["mirantis"], "release": "5.1", "fuellib_sha": "8bffb2a4723109614aeaabaabffa3c94a1b72705"}

but when I try to run ./upgrade.sh for 5.0.1 - pre checks failed with
2014-07-25 11:31:37 INFO 26872 (before_upgrade_checker) Check upgrade versions
2014-07-25 11:31:37 ERROR 26872 (cli) Cannot upgrade to the same version of fuel 5.0.1 -> 5.0.1
Traceback (most recent call last):
  File "/var/tmp/5.0.1/upgrade/site-packages/fuel_upgrade/cli.py", line 148, in main
    run_upgrade(parse_args())
  File "/var/tmp/5.0.1/upgrade/site-packages/fuel_upgrade/cli.py", line 141, in run_upgrade
    upgrade_manager.run()
  File "/var/tmp/5.0.1/upgrade/site-packages/fuel_upgrade/upgrade.py", line 48, in run
    self.before_upgrade()
  File "/var/tmp/5.0.1/upgrade/site-packages/fuel_upgrade/upgrade.py", line 74, in before_upgrade
    checker.check()
  File "/var/tmp/5.0.1/upgrade/site-packages/fuel_upgrade/before_upgrade_checker.py", line 211, in check
    raise errors.WrongVersionError(err_msg)
WrongVersionError: Cannot upgrade to the same version of fuel 5.0.1 -> 5.0.1
Upgrade failed

Here we can see that we can retrieve current version with success,
2014-07-25 11:31:36 DEBUG 26872 (config) Retrieve version from /etc/fuel/version.yaml, version is 5.1
2014-07-25 11:31:37 DEBUG 26872 (before_upgrade_checker) config in checks ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattr__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_config']
2014-07-25 11:31:37 DEBUG 26872 (before_upgrade_checker) config in checks ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattr__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_config']
2014-07-25 11:31:37 DEBUG 26872 (upgrade) Run before upgrade actions
2014-07-25 11:31:37 INFO 26872 (before_upgrade_checker) Check if devices have enough free space
2014-07-25 11:31:37 DEBUG 26872 (before_upgrade_checker) Required spaces from upgrade engines [{'/etc/yum.repos.d/5.0.1_nailgun.repo': 10}, {'/var/lib/docker': 4949, '/etc/fuel/': 10, '/etc/supervisord.d/': 10, '/var/lib/fuel_upgrade/5.0.1': 50}, {'/var/www/nailgun/5.0.1_bootstrap': 164}, {'/var/www/nailgun/5.0.1/centos': 1194, '/etc/puppet/5.0.1/modules': 4, '/etc/puppet/5.0.1/manifests': 0, '/var/www/nailgun/5.0.1/ubuntu': 784}]

But then return false-positive results

Steps to Reproduce:
deploy 5.0.1 master node - upgrade to 5.1 - upgrade to 5.0.1

[Evgeniy L (rustyrobot)]

JFYI there is workaround, you can use --no-check parameter to run upgrade.sh

[Evgeniy L (rustyrobot)]

It's is the same problem as in bug https://bugs.launchpad.net/fuel/+bug/1349833
there was failed upgrade 5.0.1 -> 5.0.1, and version which upgrade was ran from was saved in special directory and it wasn't cleaned up.

Will mark this bug as duplicate.