Exit the user entrypoint on non-zero exit code

Previously, when bundle failed following ManageIQ#528, the script continued
and finished the build.  It's unclear if the psych 5 error mattered
because our build still finished but we probably want to fail builds
and fix issues if the entrypoint script encounters non-zero exit codes.

Pull ManageIQ#546 fixed the psych 5 issue and describes the issue of the silent
error.

container-assets/user-entrypoint.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-
+set -e
 export GEM_HOME=$(ruby -e 'puts Gem.user_dir')
 export PATH=$GEM_HOME/bin:$HOME/bin:$PATH