Also drop now needless etc/promise directory.

As possible cover promises in tests.

It comes with needed check_command_execute promise plugin.

runTestSuite.in uses _update_hash_filename_ compatbility to avoid clash with
section's filename key.

As software.cfg is extended by other software releases rename the template
part to template-neo in order to avoid clash of sections.

instance.cfg md5sum has been omitted.

_update_hash_filename_ key is used to avoid clash with recipe.

hexagonit.recipe.download is replaced with slapos.recipe.build:download in
order to have the same approach everywhere and so _update_hash_filename_ key is
used to avoid collision with section:filename.

Use _update_hash_filename_ to avoid filename clash with recipes.

_update_hash_filename_ is used to avoid conflict of section:filename key with
hexagonit.recipe.download

A lot recipes treats filename key as something special, so for them support
additional key _update_hash_filename_, in order to avoid such clash.

This test just update slave dict of the class, so it is needed to request.

As timeout is the same on frontend caddy, ATS and backend caddy allow
0 or 1 accesses to the additional endpoints. The request might not reach
the backend caddy, and this is expected.

/reviewed-on nexedi/slapos!647