Revert "common/io: Keep queue buffer size multiple of 4K"

Revert "common/io: Keep queue buffer size multiple of 4K"

This reverts commit 5e9b1a7e24d058ff88aaa0563db36a804e866fa9.

This is not the best approach.  Allowing queue buffer size to grow
indefinitely causes large number of CTDB packets to be queued up very
quickly which when processed via immediate events will block CTDB from
processing events from other FDs.  If there are immediate events queued
up, tevent will never process any of the FDs till all immediate events
are processed.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>