Update grub-ec2.cfg

updating the grub config to use the nvme defaults required by aws. Should solve the failure to pass status checks. (eventually)
This only works on kernel version above 4.15. (core timeout max is 255 for below 4.15)

coreos/bugs#2464
coreos/bugs#2484
coreos/bugs#2371
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/nvme-ebs-volumes.html#timeout-nvme-ebs-volumes

coreos-base/oem-ec2-compat/files/grub-ec2.cfg

@@ -4,10 +4,10 @@ set oem_id="ec2"
 
 # Blacklist the Xen framebuffer module so it doesn't get loaded at boot
 # Disable `ens3` style names, so eth0 is used for both ixgbevf or xen.
-set linux_append="modprobe.blacklist=xen_fbfront net.ifnames=0"
+set linux_append="modprobe.blacklist=xen_fbfront net.ifnames=0 nvme_core.io_timeout=255 nvme_core.max_retries=10"
 
 if [ "$grub_platform" = pc ]; then
-	set linux_console="console=ttyS0,115200n8"
+	set linux_append="console=ttyS0,115200n8"
 	serial com0 --speed=115200 --word=8 --parity=no
 	terminal_input serial_com0
 	terminal_output serial_com0