Install also both pip2 and pip3 in every image, just for CI tests

Dockerfile

@@ -41,7 +41,7 @@ RUN yum -y --nogpg install \
     krb5-server krb5-workstation \
     less libacl-devel libgfortran libtool \
     nano \
-    parallel perl-Test-Harness python2 python3 \
+    parallel perl-Test-Harness python2 python2-pip python3 python3-pip \
     redhat-lsb-core rpm-build \
     sudo \
     vim \

Dockerfile.local

@@ -32,7 +32,8 @@ RUN adduser eos-user
 ENV XRD_VERSION 4.11.3
 RUN yum -y --nogpg update \
     && yum -y --nogpg install \
-    initscripts less heimdal-server heimdal-workstation krb5-server krb5-workstation python2 python3 \
+    initscripts less python2 python2-pip python3 python3-pip \
+    heimdal-server heimdal-workstation krb5-server krb5-workstation \
     eos-server eos-testkeytab quarkdb \
     xrootd-$XRD_VERSION \
     xrootd-client-$XRD_VERSION \

Dockerfile_asan

@@ -41,7 +41,7 @@ RUN yum -y --nogpg install \
     krb5-server krb5-workstation \
     less libacl-devel libgfortran libtool \
     nano \
-    parallel perl-Test-Harness python2 python3 \
+    parallel perl-Test-Harness python2 python2-pip python3 python3-pip \
     redhat-lsb-core rpm-build \
     sudo \
     vim \

Dockerfile_c8

@@ -41,7 +41,7 @@ RUN dnf -y install epel-release \
     krb5-server krb5-workstation \
     less libacl-devel libgfortran libtool \
     nano \
-    parallel perl-Test-Harness python2 python3 \
+    parallel perl-Test-Harness python2 python2-pip python3 python3-pip \
     redhat-lsb-core rpm-build rsync \
     sqlite sudo \
     vim \

Dockerfile_coverage

@@ -41,7 +41,7 @@ RUN yum -y --nogpg install \
     krb5-server krb5-workstation \
     lcov less libacl-devel libgfortran libtool \
     nano \
-    parallel perl-Test-Harness python2 python3 \
+    parallel perl-Test-Harness python2 python2-pip python3 python3-pip \
     redhat-lsb-core rpm-build \
     sudo \
     vim \

Dockerfile_ubuntu_bionic

@@ -38,7 +38,7 @@ RUN apt-get install -y software-properties-common \
     krb5-admin-server krb5-kdc krb5-user \
     libpam-ccreds libpam-krb5 libtool \
     nano \
-    parallel perl python2.7 python3 \
+    parallel perl python2.7 python-pip python3 python3-pip \
     rsync \
     sqlite3 \
     vim \

Dockerfile_xrd_testing

@@ -41,7 +41,7 @@ RUN yum -y --nogpg install \
     krb5-server krb5-workstation \
     less libacl-devel libgfortran libtool \
     nano \
-    parallel perl-Test-Harness python2 python3 \
+    parallel perl-Test-Harness python2 python2-pip python3 python3-pip \
     redhat-lsb-core rpm-build \
     sudo \
     vim \