Do not use vga=xxx options

Looks like syslinux 6.04-pre has trouble with these: the system gets
confused at boot in some cases and starts asking the user what to do.

Signed-off-by: Evgenii Shatokhin <eugene.shatokhin@rosalab.ru>

diff -Naur livecd-tools-21.1-rosa-patches.orig/imgcreate/live.py livecd-tools-21.1-rosa-patches/imgcreate/live.py
--- livecd-tools-21.1-rosa-patches.orig/imgcreate/live.py	2016-12-03 17:28:22.000000000 +0300
+++ livecd-tools-21.1-rosa-patches/imgcreate/live.py	2017-02-11 17:16:59.187698760 +0300
@@ -602,7 +602,7 @@
                                            liveargs = kern_opts,
                                            long = "Start " + long,
                                            short = "linux" + index,
-                                           extra = "rhgb splash=silent logo.nologo vga=788",
+                                           extra = "rhgb splash=silent logo.nologo",
                                            help = "",
                                            index = index))
             kern_opts = kernel_options + " install"
@@ -613,7 +613,7 @@
                                            liveargs = kern_opts,
                                            long = "Install " + long,
                                            short = "linux" + index,
-                                           extra = "rhgb splash=silent logo.nologo vga=788",
+                                           extra = "rhgb splash=silent logo.nologo",
                                            help = "",
                                            index = index))
             linux.append(self.__get_image_stanza(is_xen, isDracut,
@@ -622,7 +622,7 @@
                                            liveargs = kern_opts,
                                            long = "Install " + long + " in basic graphics mode",
                                            short = "basic" + index,
-                                           extra = "xdriver=vesa plymouth.enable=0 nomodeset vga=792",
+                                           extra = "xdriver=vesa plymouth.enable=0 nomodeset",
                                            help = "Try this option out if you're having trouble installing.",
                                            index = index))
             kern_opts = kernel_options
@@ -848,7 +848,7 @@
             cfg += self.__get_efi_image_stanza(fslabel = self.fslabel,
                                                liveargs = kernel_options,
                                                long = "Install " + long + " in basic graphics mode",
-                                               extra = "install nomodeset plymouth.enable=0 vga=792", index = index)
+                                               extra = "install nomodeset plymouth.enable=0", index = index)
 
             break