Problem:
The "Innodb Merge Temp File" as reported in a wait which is part of an InnoDB
Online Alter Table is reported as
data_dir/Innodb Merge Temp File" while an
"lsof +L1" during an online alter table shows that two temp files are created
in @@tmpdir instead of in the @@datadir

Fix:
added the current path when calling PSI_FILE_CALL

Follow up fix.

Reviewed by by aditya <aditya.a@oracle.com>
RB#20302