iptables-nmap: Switch to http to avoid errors on QEMU

Test case of iptables-nmap fails on SDK with error

Unable to apt-get update in lxc container
Certificate verification failed: The certificate is NOT trusted. The
certificate issuer is unknown.  Could not handshake: Error in the
certificate verification. [IP: 199.232.142.132 443]

Since the problem is only present on QEMU without a clear cause, after
checking that clock time is OK workaround it by using http instead of
https.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

lava/iptables-nmap.yaml

@@ -41,4 +41,4 @@ protocols:
     template: debian
     distribution: debian
     release: buster
-    mirror: https://deb.debian.org/debian
+    mirror: http://deb.debian.org/debian