bootloader: Cleanup splash in 50-bootargs

The 'splash' boot argument must be cleared so that it is not enabled
for rootfs and livecd that do not have plymouth installed.

features.in/bootloader/rootfs/image-scripts.d/50-bootargs

@@ -1,7 +1,9 @@
 #!/bin/sh -eu
 
-if [ -n "${GLOBAL_BASE_BOOTARGS-}" ]; then
-    if [ -s /etc/sysconfig/grub2 ]; then
+if [ -s /etc/sysconfig/grub2 ]; then
+    # Cleanup
+    sed -i "s/ splash//g" /etc/sysconfig/grub2
+    if [ -n "${GLOBAL_BASE_BOOTARGS-}" ]; then
         sed -Ei \
             "s/(GRUB_CMDLINE_LINUX_DEFAULT=)(.*)(['\"])/\1\2 $GLOBAL_BASE_BOOTARGS\3/" \
             /etc/sysconfig/grub2