We have to delete the allocated interrupt info if __inject_vm() fails.

Otherwise user space can keep flooding kvm with floating interrupts and
provoke more and more memory leaks.
Reported-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # v3.15+
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>