fix mms-agent recipe to not clobber the whole installation dir:

The existing installation process blows away its installation dir, which is not
polite if it's /usr/local/share (which is the default); plenty of other
software installs stuff there.

Changes:
- mms_agent.install_dir now correctly points to the actual install dir, and not
  its parent
- use chef's file cache instead of /tmp
- improved handling of installation dir
- both the installation and use of munin is now configurable via attribute
initial chefspecs for mms-agent recipe (ubuntu only)
improvements:

- use the new `node['mongodb']['config']['logpath']` attribute
- marked as pending test that actually modifies the host machine
added new attribute , in case the agent download fails
Revert "added new attribute , in case the agent download fails"

This reverts commit 057be15cfeab76dfc4b7c2a8077fe52cbc363e78.
Merge pull request #183 from mattchukabam/mms-agent-installation-fix

fix mms-agent recipe to not clobber the whole installation dir: