We need to hide "modprobe efivars" error output to avoid confusion. So
consolidate grub_util_exec_* into single function that can optionally redirect
all three standard descriptors and make all other functions compatibility
wrappers.
Also remove include/grub/osdep/exec_unix.h which does not appear to be used
anywhere.
references to mdadm from otherwise generic code.
(grub_util_exec_pipe): Likewise.
(grub_util_exec_pipe_stderr): Likewise.
* grub-core/osdep/unix/getroot.c (grub_util_pull_lvm_by_command):
This function calls vgs, not mdadm; adjust variable names
accordingly.
the function of these files exceeds what can be sanely handled in shell
in posix-comaptible way. Also writing it in C extends the functionality
to non-UNIX-like OS and minimal environments.
