Make sure samba{,4}-winbind-krb5-locator package is not used with trusts

Since use of winbind on FreeIPA server that is configured with trusts is
conflicting with krb5 locator based on winbind, use alternatives mechanism
to turn off the locator plugin by symlinking it to /dev/null.

https://fedorahosted.org/freeipa/ticket/3102

freeipa.spec.in

@@ -231,6 +231,13 @@ Requires: samba4
 Requires: samba4-winbind
 %endif
 Requires: libsss_idmap
+# We use alternatives to divert winbind_krb5_locator.so plugin to libkrb5
+# on the installes where server-trust-ad subpackage is installed because
+# IPA AD trusts cannot be used at the same time with the locator plugin
+# since Winbindd will be configured in a different mode
+Requires(post): %{_sbindir}/update-alternatives
+Requires(postun): %{_sbindir}/update-alternatives
+Requires(preun): %{_sbindir}/update-alternatives
 
 %description server-trust-ad
 Cross-realm trusts with Active Directory in IPA require working Samba 4 installation.
@@ -439,6 +446,9 @@ install -m 0644 init/systemd/ipa.conf.tmpfiles %{buildroot}%{_sysconfdir}/tmpfil
 mkdir -p %{buildroot}%{_localstatedir}/run/
 install -d -m 0700 %{buildroot}%{_localstatedir}/run/ipa_memcached/
 
+mkdir -p %{buildroot}%{_libdir}/krb5/plugins/libkrb5
+touch %{buildroot}%{_libdir}/krb5/plugins/libkrb5/winbind_krb5_locator.so
+
 %if 0%{?fedora} >= 16
 # Default to systemd initscripts for F16 and above
 mkdir -p %{buildroot}%{_unitdir}
@@ -569,6 +579,22 @@ if [ $? == 0  -a "${SELINUXTYPE}" == targeted -a -f ${FILE_CONTEXT}.%{name} ]; t
        rm -f ${FILE_CONTEXT}.%name
 fi
 fi
+
+%postun server-trust-ad
+if [ "$1" -ge "1" ]; then
+	if [ "`readlink %{_sysconfdir}/alternatives/winbind_krb5_locator.so`" == "/dev/null" ]; then
+		%{_sbindir}/alternatives --set winbind_krb5_locator.so /dev/null
+	fi
+fi
+
+%post server-trust-ad
+%{_sbindir}/update-alternatives --install %{_libdir}/krb5/plugins/libkrb5/winbind_krb5_locator.so \
+				winbind_krb5_locator.so /dev/null 90
+
+%preun server-trust-ad
+if [ $1 -eq 0 ]; then
+	%{_sbindir}/update-alternatives --remove winbind_krb5_locator.so /dev/null
+fi
 %endif
 
 
@@ -734,6 +760,7 @@ fi
 %{_mandir}/man1/ipa-adtrust-install.1.gz
 %{python_sitelib}/ipaserver/dcerpc*
 %{python_sitelib}/ipaserver/install/adtrustinstance*
+%ghost %{_libdir}/krb5/plugins/libkrb5/winbind_krb5_locator.so
 %endif
 
 %files client
@@ -787,6 +814,10 @@ fi
 %ghost %attr(0644,root,apache) %config(noreplace) %{_sysconfdir}/ipa/ca.crt
 
 %changelog
+* Wed Oct 10 2012 Alexander Bokovoy <abokovoy@redhat.com> - 2.99.0-50
+- Make sure server-trust-ad subpackage alternates winbind_krb5_locator.so
+  plugin to /dev/null since they cannot be used when trusts are configured
+
 * Wed Oct 10 2012 Petr Viktorin <pviktori@redhat.com> - 2.99.0-49
 - Add zip dependency, needed for creating unsigned Firefox extensions