add rpmdevtools as build dep for el5

9feb9cf4 added rpmdevtools as an install depedency;
it is also needed as a build dep for current functional tests.

hacking/titotest-centos-5.9/Dockerfile

@@ -10,6 +10,7 @@ RUN yum -y install git rpm-build \
     python-devel python-nose python-setuptools python-pep8 \
     python-pip \
     docbook-style-xsl \
+    rpmdevtools \
     libxslt asciidoc tar createrepo which python-bugzilla
 
 RUN pip-python install mock --upgrade

tito.spec

@@ -17,6 +17,7 @@ BuildRequires: python-setuptools
 BuildRequires: asciidoc
 BuildRequires: docbook-style-xsl
 BuildRequires: libxslt
+BuildRequires: rpmdevtools
 
 Requires: python-setuptools
 Requires: python-bugzilla