ONLY WHEN SYNCING BINLOG

Problem: binlog_group_commit_sync_delay is getting applied
to every binary log commit group.

Analysis: binlog_group_commit_sync_delay variable is introduced to
control how many microseconds the binary log commit waits before
synchronizing the binary log file to disk. sync_binlog variable
is introduced to control the number of binary log commit groups
to collect before synchronizing the binary log to disk

In the current code, server is waiting for binlog_group_commit_sync_delay
microseconds after entering into the sync stage of every group
i.e., every leader of BGC group is waiting the specified time. In case
of sync_binlog > 1 case or sync_binlog=0 case that every leader will not
be doing 'sync' and users expectation will be that those groups that are
doing sync will *only* hit the waiting period.

Fix: wait_count_or_timeout logic should be protected in such a way that
it will enter only if the sync stage is going to do the sync i.e.,
check if sync_counter reaches sync_binlog value, only then call the
wait_count_or_timeout function.