engine: Rename UseSecureConnectionWithServers

Rename UseSecureConnectionWithServers to EncryptHostCommunication to be
more descriptive.

Change-Id: Ia25ed8e39a1a0bc737fb198e90d92489a8fe346c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1003117
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>