(QENG-1182) Add node to classifier prior to adding pe_repo class

Prior to this commit, beaker would make the assumption that a node had
already checked into the classifier. This commit changes that by
ensuring that the node is in the classifier before giving it the pe_repo
class.
Merge pull request #443 from briancain/maint/master/add-node-to-classifier

(QENG-1182) Add node to classifier prior to adding pe_repo class
(maint) Bump version for 1.17.7 release
Merge pull request #444 from branan/ship_1_17_7

(maint) Bump version for 1.17.7 release
(QENG-1186) Fix Beaker::DSL:Helpers.puppet_{user,group}

Looks like the contents of these methods were mixed upwhen originally written.
Luckily the puppet user is usually the same as the puppet group.

Signed-off-by: Wayne <wayne@puppetlabs.com>