Check for curl failure (#521)

When running the peadm::agent_install shell task, fail the
task if the curl command fails.

Author: seanmil

tasks/agent_install.sh

@@ -1,11 +1,12 @@
 #!/bin/bash
 
 set -e
+set -o pipefail
 
 if [ -x "/opt/puppetlabs/bin/puppet" ]; then
   echo "WARNING: Puppet agent is already installed. Re-install, re-configuration, or upgrade not supported and might fail."
 fi
 
 flags=$(echo "$PT_install_flags" | sed -e 's/^\["*//' -e 's/"*\]$//' -e 's/", *"/ /g')
 
-curl -k "https://${PT_server}:8140/packages/current/install.bash" | bash -s -- $flags
+curl --fail -k "https://${PT_server}:8140/packages/current/install.bash" | bash -s -- $flags