Fix utils.system.Bootloader().Arguments()

rstrip so we dont' remove leading indentation, and check whether
a newline is present before we add it to grub_cfg. If not, add one

Change-Id: Idc064a456ae8662bf4f8cebd88a19107ca611608
Signed-off-by: Ryan Barry <rbarry@redhat.com>
Have the custom device dialog move to the next page all the time

Previously, the custom device dialog didn't move to the next plugin
on the installation device page, though it did on the boot device page.
Do so to maintain consistent behavior.

Change-Id: I075e8c9eed82ce0507eee7e878dbefdcb3ecdb23
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1065915
Signed-off-by: Ryan Barry <rbarry@redhat.com>
Catch already selected disks in "Other Devices" in installation

Check whether or not the entered device has already been selected
in the table on the installation page, so we cannot end up in a
state where the same disk is present in the list of devices to
install to multiple times.

Change-Id: Iee4d32c94f5906c33b353aef45180fcc3eb594de
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1113026
Signed-off-by: Ryan Barry <rbarry@redhat.com>