cmd/root: Don't validate subordinate IDs when generating the completions

Ever since commit bafbbe8, the shell completions are generated
while building Toolbx using the 'completion' command.  This involves
running toolbox(1) itself, and hence validating the subordinate user and
group ID ranges.

Unfortunately, some build environments don't have subordinate ID ranges
set up.  Therefore, it's better to avoid validating them when generating
the shell completions, especially, since they are generated by Cobra
itself and subordinate ID ranges are not involved at all.

Note that subordinate ID ranges may be needed when the generated shell
completions are actually used in interactive command line environments.
The shell completions invoke the hidden '__complete' command to get the
results that are presented to the user, and, if needed, the subordinate
ID ranges will continue to be used by podman(1) as part of that.

Some changes by Debarshi Ray.

containers#1246

src/cmd/root.go

@@ -401,6 +401,11 @@ func validateSubIDRanges(cmd *cobra.Command, args []string, user *user.User) (bo
 		return true, nil
 	}
 
+	if cmdName, completionCmdName := cmd.Name(), completionCmd.Name(); cmdName == completionCmdName {
+		logrus.Debugf("Look-up not needed: command %s doesn't need them", cmdName)
+		return true, nil
+	}
+
 	if _, err := utils.ValidateSubIDRanges(user); err != nil {
 		logrus.Debugf("Looking for sub-GID and sub-UID ranges: %s", err)
 		return false, newSubIDError()