Proposed upstream patch dropping the iptables-ipv6 requirement on Fedora >= 17 and RHEL >= 7:
https://www.redhat.com/archives/libvir-list/2014-July/msg00371.html

Now pushed:
commit 66e706121045b965c7c469aebc28c6f258577cd4
Author:     Ján Tomko <jtomko@redhat.com>
CommitDate: 2014-07-08 15:29:46 +0200

    Don't require iptables-ipv6 on >= F17 and RHEL >= 7
    
    We only need ip6tables, which is now a part of the iptables package:
    http://pkgs.fedoraproject.org/cgit/iptables.git/commit/?h=1392835
    
    This needlessly pulls in iptables-services:
    https://bugzilla.redhat.com/show_bug.cgi?id=1101510
    which can conflict with firewalld:
    https://bugzilla.redhat.com/show_bug.cgi?id=1101484

git describe: v1.2.6-77-g66e7061

Related:  In F20, when you press the windows key and type "firew", two firewall icons come up.  This can be fixed without removing other packages you don't want to remove only by going outside of yum and using rpm -e --nodeps iptables-services .

When this patch is approved and released to F20, how will iptables-services get removed for those who did not explicitly install it, and not get removed for those who did?

This patch is not planned for F20. Are you experiencing the issues from bug 1101484 on F20?

Yum does not clean up old dependencies by default, I think the "clean_requirements_on_remove" option in yum.conf can do that.

Verify as below

Tested build:
libvirt-1.2.8-7.el7.src.rpm

<1> Download libvirt-1.2.8-7.el7.src.rpm on rhel6.6, after installing, the code lines have been integrated.
[root@ibm-x3850x5-06 rpmbuild]# pwd
/root/rpmbuild
[root@hp-dl385g7-09 rpmbuild]# cat SPECS/libvirt.spec | grep iptables-ipv6 -b3
31184-BuildRequires: dnsmasq >= 2.41
31215-BuildRequires: iptables
31239-    %if (0%{?fedora} && 0%{?fedora} < 17) || (0%{?rhel} && 0%{?rhel} < 7)
31313:BuildRequires: iptables-ipv6
31342-    %endif
31353-BuildRequires: radvd
31374-%endif
--
37475-Requires: radvd
37491-Requires: iptables
37510-            %if (0%{?fedora} && 0%{?fedora} < 17) || (0%{?rhel} && 0%{?rhel} < 7)
37592:Requires: iptables-ipv6
37616-            %endif
37635-
37636-%description daemon-driver-network
--
37978-Requires: libvirt-daemon = %{version}-%{release}
38027-Requires: iptables
38046-            %if (0%{?fedora} && 0%{?fedora} < 17) || (0%{?rhel} && 0%{?rhel} < 7)
38128:Requires: iptables-ipv6
38152-            %endif
38171-Requires: ebtables
38190-

<2>Rebuild package on rhel6.6, the missing iptables-ipv6 will be listed in dependencies list.
[root@hp-dl385g7-09 rpmbuild]# uname -r
2.6.32-504.4.1.el6.x86_64
[root@hp-dl385g7-09 rpmbuild]# rpm -qa | grep iptables
iptables-1.4.7-14.el6.x86_64
[root@hp-dl385g7-09 rpmbuild]# rpmbuild -bp SPECS/libvirt.spec 
error: Failed build dependencies:
	autoconf is needed by libvirt-1.2.8-7.el6.x86_64
	automake is needed by libvirt-1.2.8-7.el6.x86_64
...
	iptables-ipv6 is needed by libvirt-1.2.8-7.el6.x86_64
...
	systemtap-sdt-devel is needed by libvirt-1.2.8-7.el6.x86_64
	scrub is needed by libvirt-1.2.8-7.el6.x86_64

<3>Rebuild package on rhel7.1, can pass the dependencies checking.
[root@ibm-x3850x5-06 rpmbuild]# uname -r
3.10.0-196.el7.x86_64

[root@ibm-x3850x5-06 rpmbuild]# rpm -qa | grep iptables
iptables-services-1.4.21-13.el7.x86_64
iptables-1.4.21-13.el7.x86_64

[root@ibm-x3850x5-06 rpmbuild]# rpmbuild -bp SPECS/libvirt.spec 
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.Awp9sK
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf libvirt-1.2.8
+ /usr/bin/gzip -dc /root/rpmbuild/SOURCES/libvirt-1.2.8.tar.gz
+ /usr/bin/tar -xf -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd libvirt-1.2.8
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ PATCHCOUNT=217
+ PATCHLIST=/tmp/lua_XQUBfS
+ git init -q
+ git config user.name rpm-build
+ git config user.email rpm-build
+ git config gc.auto 0
+ git add .
+ git commit -q -a --author 'rpm-build <rpm-build>' -m 'libvirt-1.2.8 base'
++ grep '\.patch$' /tmp/lua_XQUBfS
++ wc -l
+ COUNT=217
+ '[' 217 -ne 217 ']'
+ '[' 217 -gt 0 ']'
+ xargs git am
Applying: RHEL: screenshot: Implement multiple screen support
...

We can get expected results, move to Verified.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2015-0323.html