rest: fix rsdl for cloud-init parameters

fix error with brackets in cloud init parameters for run vm rsdl
definition.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=990572
Change-Id: Ia030c57d7315f8c55e384c79e207144bc5f7e4a9
Signed-off-by: Omer Frenkel <ofrenkel@redhat.com>