tests: add missing dependency iptables

KDC proxy tests are using iptables, but this is optional package in at
least Fedora cloud image, thus we must have it in dependencies

Reviewed-By: Tomas Krizek <tkrizek@redhat.com>

freeipa.spec.in

@@ -772,6 +772,7 @@ Requires: python-pytest-sourceorder
 Requires: ldns-utils
 Requires: python-sssdconfig
 Requires: python2-cryptography >= 1.6
+Requires: iptables
 
 Provides: %{alt_name}-tests = %{version}
 Conflicts: %{alt_name}-tests
@@ -806,6 +807,7 @@ Requires: python3-pytest-sourceorder
 Requires: ldns-utils
 Requires: python3-sssdconfig
 Requires: python3-cryptography >= 1.6
+Requires: iptables
 
 %description -n python3-ipatests
 IPA is an integrated solution to provide centrally managed Identity (users,