Need updated pxegrub file to address OS-3634 and OS-3635

[nshalman]

OS-3634 and OS-3635 improve how grub deals with serial ports.
Someone on IRC ran into a problem that was addressed by replacing the current tftpboot/pxegrub file with a fresh one from the proto dir of a platform build.

Quick fix is to grab a fresh one and check it in.
A more thorough though more complicated fix is to package up pxegrub in the boot tarball generated by the build process (tweak a manifest in illumos-joyent e.g. nshalman/illumos-joyent@c772887) and then have sdc-booter somehow grab pxegrub out of that as a build step.

[trentm]

@rgulewich ping, thoughts?

[sperreault]

Could we just use a quick fix here and copy a pxegrub file that works (i'm doing this manually right now)

[nshalman]

I agree. One of these two tickets (this one and #2) should be fixed by checking in a working binary. The other could be left open for the possibility of the fancier fix.

[nshalman]

RELENG-608 (TritonDataCenter/illumos-joyent@62890e2) provides the raw materials for both the quick fix and the better fix.

[nshalman]

@jclulow I just noticed https://smartos.org/bugview/HEAD-2315

While you're doing GRUB related stuff, perhaps you could take a look at this issue.