Add support for UEFI operating systems returned by os-prober

os-prober returns UEFI operating systems in the form:

path:long-name:name

where path is the path under the EFI directory on the ESP. This is in
contrast to legacy OSes, where path is the device string. Handle this case.
Disable GRUB video support for IBM power machines

Should fix the problem in bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=973205
Revert "Add bootpath device to the list" (#967862)

commit c6e8465f fixes this issue.

This reverts commit a2780be06f7de35a0dd4cc19a68b151176707ae7.
Fix net_bootp cmd crash when there isn't network card

Adds a check for a network card available before trying to procedure with bootp.

This fixes the bugzilla bellow:
Bug 960624 - Grub2 crashes when net_bootp command fails
https://bugzilla.redhat.com/show_bug.cgi?id=960624