core: edit host "advanced" parameters to change protocol

Editting host protocol was no possible. This patch enables chaning
protocol for host in maintanace mode only. After the change connection
is closed and new protocol is used when reconnecting.

Bug-Url: https://bugzilla.redhat.com/1124442
Change-Id: I8cbd88616ae156209deb3b4841fa6a67d93267f0
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>