Agent installation fails with the following error:
Additional kernel packages to be installed : linux-headers-3.11.0-15-generic Installing required packages...
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package linux-headers-3.11.0-15-generic is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or is only available from another source
E: Package 'linux-headers-3.11.0-15-generic' has no installation candidate Cleaning working directories...