Custom policy for ssh-keygen failure

This patch contains a custom policy to allow ssh-keygen to write to
/tmp. This action is blocked by SELinux. The custom policy is needed
until the upstream SELinux policy is updated for Fedora or nova is
modified to call ssh-keygen to write out to a different directory.

Partial-Bug: 1284485
Change-Id: I59de4e88d9343e093a95436432e2e4d68f425d06
Merge "Custom policy for ssh-keygen failure"