QEMU: Relax version number parsing

Roman Shaposhnik reports:

  Here's what I'm getting on the kvm-qemu side of things:

  # capstan run cloudius/osv
  Created instance: cloudius-osv

  exec: "qemu-system-x86_64": executable file not found in $PATH

  Which is fine, since it seems like on RHEL the relevant thing is
  called kvm-qemu.

  At least that's what virsh is using. capstan, however, doesn't seem to
  like it:

  # ln -s /usr/libexec/qemu-kvm /usr/bin/qemu-system-x86_64
  # Created instance: cloudius-osv

  unable to parse QEMU version from 'QEMU PC emulator version 0.12.1
  (qemu-kvm-0.12.1.2), Copyright (c) 2003-2008 Fabrice Bellard'

  Any advice? I must be not the first one trying to run this on
  RHEL/CentOS6.

Fix the problem by relaxing QEMU version parsing regexp.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>