Revert "configure: Virtfs doesn't require libcap." This reverts commit d10f9056bacf7991fd6a5f63ac2e0190e84ea3a7 due to a build breakage. See http://spunk.home.kraxel.org/bb/builders/ubuntu-default/builds/52 Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>