dialplan: add reload_delta parameter

[marcocapetta]

Pre-Submission Checklist

• Commit message has the format required by CONTRIBUTING guide
• Commits are split per component (core, individual modules, libs, utils, ...)
• Each component has a single commit (if not, squash them into one commit)
• No commits to README files for modules (changes must be done to docbook files
  in doc/ subfolder, the README file is autogenerated)

Type Of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)

Checklist:

• PR should be backported to stable branches
• Tested changes locally
• Related to issue #XXXX (replace XXXX with an open issue number)

Description

In commit 99d5da8 a mechanism for basic safety in case of concurent rpc reload were added. This works fine but it is limiting our test scenarios where multiple changes should happen quickly.

The new dialplan paramenter reload_delta allows everyone to configure rpc reload rate limit to the preferred number of seconds.
In case the parameter is not specified. the default value is 5 seconds.

[linuxmaniac]

I would say We should not backport this change since this is a new parameter and no new features should go to stable releases

[linuxmaniac]

Thanks! :-)