Update Fedora and CentOS docker images.

- Reduce image size by skipping weak package references.
- Consolidate and sort packages to install.
- Improve consistency between versions.
- Combine yum/dnf install and clean to avoid unwanted caching.
- Don't update existing packages from base image unnecessarily.

test/utils/docker/fedora23/Dockerfile

@@ -1,6 +1,5 @@
-# Latest version of fedora 23
 FROM fedora:23
-RUN dnf -y update; dnf clean all
+
 RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i == systemd-tmpfiles-setup.service ] || rm -f $i; done); \
 rm -f /lib/systemd/system/multi-user.target.wants/*; \
 rm -f /etc/systemd/system/*.wants/*; \
@@ -9,24 +8,26 @@ rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
 rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
 rm -f /lib/systemd/system/basic.target.wants/*; \
 rm -f /lib/systemd/system/anaconda.target.wants/*;
-RUN dnf -y install \
+
+RUN dnf clean all && \
+    dnf -y --setopt=install_weak_deps=false install \
     acl \
     asciidoc \
-    dbus-python \
     bzip2 \
+    dbus-python \
     file \
     findutils \
-    glibc-common \
     git \
     iproute \
     make \
-    mercurial \
     mariadb-server \
+    mercurial \
     MySQL-python \
+    openssh-clients \
+    openssh-server \
     procps \
-    PyYAML \
-    python-coverage \
     python2-dnf \
+    python-coverage \
     python-httplib2 \
     python-jinja2 \
     python-keyczar \
@@ -36,6 +37,7 @@ RUN dnf -y install \
     python-pip \
     python-setuptools \
     python-virtualenv \
+    PyYAML \
     rpm-build \
     rubygems \
     subversion \
@@ -43,12 +45,17 @@ RUN dnf -y install \
     tar \
     unzip \
     which \
-    openssh-clients \
-    openssh-server \
     yum \
-    zip
-RUN localedef --quiet -f ISO-8859-1 -i pt_BR pt_BR
-RUN localedef --quiet -f ISO-8859-1 -i es_MX es_MX
+    zip \
+    && \
+    dnf clean all
+
+RUN dnf -y --setopt=install_weak_deps=false update glibc-common && \
+    localedef --quiet -f ISO-8859-1 -i pt_BR pt_BR && \
+    localedef --quiet -f ISO-8859-1 -i es_MX es_MX && \
+    dnf clean all
+
+RUN localedef --quiet -c -i en_US -f UTF-8 en_US.UTF-8
 RUN /usr/bin/sed -i -e 's/^\(Defaults\s*requiretty\)/#--- \1/'  /etc/sudoers
 RUN mkdir /etc/ansible/
 RUN /usr/bin/echo -e '[local]\nlocalhost ansible_connection=local' > /etc/ansible/hosts