virtcontainers/utils: Implement function to check vsocks support

Implement function to check if the system has support for vsocks.
This function looks for vsock and vhost-vsock devices returning
true if those exist, otherwise false.

Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>
Signed-off-by: Julio Montes <julio.montes@intel.com>

virtcontainers/utils/utils_test.go

@@ -294,3 +294,34 @@ func TestBuildSocketPath(t *testing.T) {
 		assert.Equal(d.expected, result)
 	}
 }
+
+func TestSupportsVsocks(t *testing.T) {
+	assert := assert.New(t)
+
+	orgVSockDevicePath := VSockDevicePath
+	orgVHostVSockDevicePath := VHostVSockDevicePath
+	defer func() {
+		VSockDevicePath = orgVSockDevicePath
+		VHostVSockDevicePath = orgVHostVSockDevicePath
+	}()
+
+	VSockDevicePath = "/abc/xyz/123"
+	VHostVSockDevicePath = "/abc/xyz/123"
+	assert.False(SupportsVsocks())
+
+	vSockDeviceFile, err := ioutil.TempFile("", "vsock")
+	assert.NoError(err)
+	defer os.Remove(vSockDeviceFile.Name())
+	defer vSockDeviceFile.Close()
+	VSockDevicePath = vSockDeviceFile.Name()
+
+	assert.False(SupportsVsocks())
+
+	vHostVSockFile, err := ioutil.TempFile("", "vhost-vsock")
+	assert.NoError(err)
+	defer os.Remove(vHostVSockFile.Name())
+	defer vHostVSockFile.Close()
+	VHostVSockDevicePath = vHostVSockFile.Name()
+
+	assert.True(SupportsVsocks())
+}