tests: Do not occlude grub-shell return code

tests: Do not occlude grub-shell return code

The script grub-shell does the bulk of the testing. If it returns an error
code, that means that the test failed and the test should immediately exit
with that error code. When grub-shell is used as a non-terminating command
in a pipeline, e.g. when data needs to be extracted from its output, its
error code will be occluded by the last command in the pipeline. Refactor
tests so that the shell will error with the exit code of grub-shell by
breaking up pipelines such that grub-shell is always the last command in
the pipeline that it is used in.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>