arch: use libc::getrandom() instead of rand crate

This removes the last use of rand in our tree and the removal of several
dependencies.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

arch/src/x86_64/interrupts.rs

@@ -84,10 +84,6 @@ pub fn set_lint(vcpu: &Arc<dyn hypervisor::Vcpu>) -> Result<()> {
 #[cfg(test)]
 #[cfg(feature = "kvm")]
 mod tests {
-
-    extern crate rand;
-    use self::rand::Rng;
-
     use super::*;
 
     const KVM_APIC_REG_SIZE: usize = 0x400;
@@ -111,8 +107,15 @@ mod tests {
 
     #[test]
     fn test_apic_delivery_mode() {
-        let mut rng = rand::thread_rng();
-        let mut v: Vec<u32> = (0..20).map(|_| rng.gen::<u32>()).collect();
+        let mut v: Vec<u32> = Vec::new();
+        v.resize(20, 0);
+
+        unsafe {
+            assert_eq!(
+                libc::getrandom(v.as_mut_ptr() as *mut _ as *mut libc::c_void, 80, 0),
+                80
+            );
+        }
 
         v.iter_mut()
             .for_each(|x| *x = set_apic_delivery_mode(*x, 2));