Securely create temp directorys / files

The temp directory packstack was using was being created in
an insecure manor with world readable permissions. This commit ensures
temp directories are created securly on both the local and remote
hosts

o Create var directory with tempfile.mkdtemp
o remove other places where var directory was created
o change permissions of all files that do (or may) contain
  sensitive data to 600
o No longer append data to mainifest file, it is now created and
  writen out in once
o Attempts to remove data on remote hosts after the packstach run

CVE-2013-0261
https://bugzilla.redhat.com/show_bug.cgi?id=908101

Change-Id: Ie7105207d3da128d630628c1df037ffafc94beb8