ui: fixing addHost form issues when playing with using host provider

Apparently hiding the host provider form was buggy. In this patch we fix
the fields cleaning and the visibility of the provider parameters.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1165670
Change-Id: I700ec281a1bd1617d0168d59c8daef5b5bcf4f6b
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>