[docs] Environment cannot be installed without access to updates repositories

[Vladimir Kuklin]

This bug is related to https://bugs.launchpad.net/fuel/+bug/1451222 and https://bugs.launchpad.net/bugs/1451502. This particulard bug-id is related to FUEL documentation.

Currently, if we install environment, we try to update repository information for all repositories including repositories with updates this leads to an issue if slave nodes cannot access updates repositories.

As an example:

Mon May 04 05:20:04 +0000 2015 Puppet (err): Execution of '/usr/bin/yum -d 0 -e 0 -y install htop' returned 1: Error: Cannot retrieve repository metadata (repomd.xml) for repository: mos-updates. Please verify its path and try again

This assumes that we should update documentation with this information, so that user can synchronize updates repositories to an accessible location prior to running deployment.