restapi :  Custom property values with multiple "=" not returned (#886802)

When setting a custom property that contains more than one '=' character, the property is saved and displayed in the web interface, but cannot be seen when getting the VM properties via the REST API.

Change-Id: I19bcbc278a51722636ddaa0a660b5289933bc8ba
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=886802
Signed-off-by: Ravi Nori <rnori@redhat.com>