chore: anticipate expected delay in tests

Author: blaggacao

nix/kexec-installer/test.nix

@@ -135,6 +135,8 @@ makeTest' {
     node1.succeed('/root/kexec/kexec --version >&2')
     node1.succeed('/root/kexec/run >&2')
 
+    time.sleep(6)
+
     # wait for kexec to finish
     while ssh(["true"], check=False).returncode == 0:
         print("Waiting for kexec to finish...")