Improve CLI help section for dsidm and general parent arguments

[droideck]

Issue Description
We have two issues that make a user's life harder when they use 389 DS CLI tools.

1. When you create an entry with dsidm, the OU where this entry is placed must exist. However, this information, and the required OUs are neither mentioned in --help, the man page, nor does the error message contains any hint.

   Suggestion:

   • dsidm should mention the required OUs both in --help and the man page.

   • It would be nice if the error message could show a meaningful error:

     Error: 105 - 4 - 32 - No such object - [] - dc=example,dc=com

     It's really not self-explaining that it means that ou={people,group,...} is missing

2. When we run:

   dsctl test db2bak -h
   usage: dsctl [instance] db2bak [-h] [archive]
   

   There is no [-v] option before instance_name mentioned, so user will not know he can use it unless he runs "dsctl -h".

   It should mention [-v] in help like this:

   usage: dsctl [-v] [instance] db2bak [-h] [archive]
   

[droideck]

BZ#1 - https://bugzilla.redhat.com/show_bug.cgi?id=2164990
BZ#2 - https://bugzilla.redhat.com/show_bug.cgi?id=2019735

[droideck]

For the second case (There is no [-v] option before instance_name mentioned), I tried different approaches, and I think we have at least three options here:

1. Just add -v and -j parameters to all of the subparsers.
   That won't actually work (or at least, I wasn't able to find how to make it work with argparse).
   If we do so, -v is accepted at this position dsctl [-v] [instance] db2bak [-h] [archive], but it's always set to the default False because -v from a subparser overwrites the value.

2. We can specify -v and -j at the shared parent parser
   It is how argparse assumes we approach the problem. It is simple, consistent and without any hacks.
   But it will bring a problem, that current way of doing things won't work anymore usage: dsctl [-v] [instance] db2bak [-h] [archive].
   Only this will work: usage: dsctl [instance] db2bak [-v] [-j] [-h] [archive]. Hence, we'll need to fix all of the WebUI cmd lines and it may break some customer's scripts.

3. We can modify the help info using the argparse.HelpFormatter implementation.
   It will give us fine-grained control over the text, and we can mention that -v and -j are accepted before the instance name.
   It is a hack, though, and we'll need to keep track of it if we make any changes in -v and -j or if argparse changes something in its implementation. So, it brings a complexity that can be avoided.

Also, it's possible that the issue "hidden parent options in a subparser usage" is already reported somewhere here - Argparse issues (view) . I might look through them later (it's a pile of chaos), but we have customers asking for a fix now. So I think we should choose the 2nd or 3rd approach.

What do you think, folks?