Revert "KVM: release anon file in failure path of vm creation"

This reverts commit 77ecc085fed1af1000ca719522977b960aa6da52.

Al Viro colorfully says: "You should *NEVER* use sys_close() on failure
exit paths like that.  Moreover, this kvm_put_kvm() becomes a double-put,
since closing the damn file will drop that reference to kvm.  Please,
revert.  anon_inode_getfd() should be used only when there's no possible
failures past its call".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>