issue: 3933912 Fix epoll ready list iteration

[pasis]

Description

The recent xlio_list change introduced a bug into epoll ready list iteration: a socket can be removed from the list before getting the next item. This leads to iteration over a removed item causing endless loop.

As a fix, remember 'si_next' before removing a socket from the list.

Also align mem_buf_desc_t to the cache line boundary.

What

Fix epoll ready list iteration

Why ?

Bugfix.

Change type

What kind of change does this PR introduce?

• [x] Bugfix
• [ ] Feature
• [ ] Code style update
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Documentation content changes
• [ ] Tests
• [ ] Other

Check list

• [ ] Code follows the style de facto guidelines of this project
• [ ] Comments have been inserted in hard to understand places
• [ ] Documentation has been updated (if necessary)
• [ ] Test has been added (if possible)

[galnoam]

@pasis, can you check cov and style?