in_tail: Add switch_io_after_read parameter. fix #2478

[repeatedly]

Signed-off-by: Masahiro Nakagawa repeatedly@gmail.com

Which issue(s) this PR fixes:
Fixes #2478

What this PR does / why we need it:
Add switch_io_after_read parameter to control IO read operation.
I tested several cases and no problem. But I can't say all environment have no problem with this change so I add parameter for smooth migration.

Docs Changes:
Will submit a PR to add parameter for v1.6.3.

Release Note:
Same as title.

[ganmacs]

According to this comment #2478 (comment), I think @fifo and the contents of a file should be flushed not to lost the data when detaching.

resolve this by setting rotate_wait to a bigger value

I think this is good for a workaround. but not for the final solution.

[ashie]

It seems that #3185 is now going to include this fix.
I'll close this if #3185 is landed with similar implementation with this.
On the other hand, it doesn't yet resolve problems mentioned in #2478 (comment), so further work is needed.

[ashie]

#3185 has been merged.
Setting read_bytes_limit_per_second to 8192 (or less than it) will take same effect with this.