TT#29456 Install unittest-xml-reporting using pip

Debian package 'python-xmlrunner' is based on old
unittest-xml-reporting (1.5.0-1) and generated report *.xml file is not
recognized by jenkins jUnit plugin:
  [xUnit] [ERROR] - The result file
  '/var/lib/jenkins/workspace/kamailio-config-tests-unit-test-docker/results/test_check.xml'
  for the metric 'JUnit' is not valid. The result file has been skipped.

So let's install the newest version from pip in docker the same like in Makefile

Change-Id: I7f4272d04bdec5ed1112bb25e751a1c4df95359b

t/Dockerfile

@@ -9,8 +9,9 @@ ENV REFRESHED_AT 2018-01-18
 
 RUN apt-get update
 RUN apt-get install --assume-yes python-yaml python-junitxml \
-	make libtemplate-perl libyaml-perl python-xmlrunner
+	make libtemplate-perl libyaml-perl python-pip
 
+RUN pip install unittest-xml-reporting
 RUN echo './t/testrunner' >>/root/.bash_history
 
 WORKDIR /code/
@@ -21,7 +22,7 @@ WORKDIR /code/
 # When you want to build the base image from scratch
 # (jump to the next section if you don't want to build yourself!):
 #
-# % docker build --tag="kamailio-config-tests-jessie" -f t//Dockerfile .
+# % docker build --tag="kamailio-config-tests-jessie" -f t/Dockerfile .
 # % docker run --rm -i -t -v $(pwd):/code:rw kamailio-config-tests-jessie:latest bash
 #
 # Use the existing docker image: