util/backoff: seed math/rand source (#5124)

It has a negligible impact, but since security scanners like gosec will pick
this up, let's do it in a way that'll pass inspection.

Signed-off-by: Stephan Renatus <stephan.renatus@gmail.com>

util/backoff.go

@@ -9,6 +9,15 @@ import (
 	"time"
 )
 
+func init() {
+	// NOTE(sr): We don't need good random numbers here; it's used for jittering
+	// the backup timing a bit. But anyways, let's make it random enough; without
+	// a call to rand.Seed() we'd get the same stream of numbers for each program
+	// run. (Or not, if some other packages happens to seed the global randomness
+	// source.)
+	rand.Seed(time.Now().UnixNano())
+}
+
 // DefaultBackoff returns a delay with an exponential backoff based on the
 // number of retries.
 func DefaultBackoff(base, max float64, retries int) time.Duration {