fixes #1657 - Support Puppet http reports processor

this patch allow usage of puppet http report processor.
in order to use it simply update your puppet.conf to have the following:

reports = http
reporturl = http://foreman/reports

NOTE: its not possible to use ssl URLS with the current report processor (AFAIK)

Send error messages through JSON instead of just {"errors":[]}

fixes #1670 - Model / OS on "Hosts" page not getting updated properly

[EC2] Adds retry on host not available, add some useful debugging.

- debugging, to get the whole message
- add backtrace to compute resource failure msg
- add debug logging for Fog errors on create

fixes #1351 New smart variable and match cannot be entered at same time.

smart vars looks sharper.

fixes #1572

fixed useless warning

fix error in validation for new compute hosts

when libvirt is not enabled, compute resource provider name is incorrect.