Do not try to typecast values with ERB

not all JSON backends will accept Strings with ERB while dumping
fixes:
- https://bugzilla.redhat.com/show_bug.cgi?id=1117178
- https://bugzilla.redhat.com/show_bug.cgi?id=1117346
- https://bugzilla.redhat.com/show_bug.cgi?id=1116966