Add RHEL 7.3 to ansible-test and CI. (#26550)

* Add support for RHEL to ansible-test.
* Enable RHEL 7.3 on Shippable.

test/runner/setup/remote.sh

@@ -28,21 +28,39 @@ if [ "${platform}" = "freebsd" ]; then
         subversion \
         sudo \
         zip
+elif [ "${platform}" = "rhel" ]; then
+    yum update -y
+
+    yum install -y \
+        gcc \
+        git \
+        mercurial \
+        python-devel \
+        python-jinja2 \
+        python-virtualenv \
+        python2-cryptography \
+        rubygems \
+        subversion \
+        unzip \
+
+    pip --version 2>/dev/null || curl --silent --show-error https://bootstrap.pypa.io/get-pip.py | python
 fi
 
-pip install virtualenv
+if [ "${platform}" = "freebsd" ] || [ "${platform}" = "osx" ]; then
+    pip install virtualenv
 
-# Tests assume loopback addresses other than 127.0.0.1 will work.
-# Add aliases for loopback addresses used by tests.
+    # Tests assume loopback addresses other than 127.0.0.1 will work.
+    # Add aliases for loopback addresses used by tests.
 
-for i in 3 4 254; do
-    ifconfig lo0 alias "127.0.0.${i}" up
-done
+    for i in 3 4 254; do
+        ifconfig lo0 alias "127.0.0.${i}" up
+    done
 
-ifconfig lo0
+    ifconfig lo0
+fi
 
 # Since tests run as root, we also need to be able to ssh to localhost as root.
-sed -i '' 's/^# *PermitRootLogin.*$/PermitRootLogin yes/;' /etc/ssh/sshd_config
+sed -i= 's/^# *PermitRootLogin.*$/PermitRootLogin yes/;' /etc/ssh/sshd_config
 
 if [ "${platform}" = "freebsd" ]; then
     # Restart sshd for configuration changes and loopback aliases to work.
@@ -65,5 +83,9 @@ fi
 cat << EOF > ~/.bashrc
 alias ls='ls -G'
 export PS1='\[\e]0;\u@\h: \w\a\]\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
-cd ~/ansible/
 EOF
+
+# Make sure ~/ansible/ is the starting directory for interactive shells.
+if [ "${platform}" = "osx" ]; then
+    echo "cd ~/ansible/" >> ~/.bashrc
+fi