src/meta-openembedded:mariadb: fix failures to start install_db.service

It fails to start install_db.service when install mariadb-setupdb from a
package repo via dnf:

root@qemux86-64:~# systemctl status install_db
x install_db.service - Install MySQL Community Server Database
     Loaded: loaded (/lib/systemd/system/install_db.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Fri 2021-07-09 02:55:12 UTC; 5s ago
    Process: 504 ExecStart=/usr/bin/mysql-systemd-start pre (code=exited, status=203/EXEC)
   Main PID: 504 (code=exited, status=203/EXEC)

Jul 09 02:55:12 qemux86-64 systemd[1]: Starting Install MySQL Community Server Database...
Jul 09 02:55:12 qemux86-64 systemd[504]: install_db.service: Failed to locate executable /usr/bin/mysql-systemd-start: No such file or directo>
Jul 09 02:55:12 qemux86-64 systemd[504]: install_db.service: Failed at step EXEC spawning /usr/bin/mysql-systemd-start: No such file or direct>
Jul 09 02:55:12 qemux86-64 systemd[1]: install_db.service: Main process exited, code=exited, status=203/EXEC
Jul 09 02:55:12 qemux86-64 systemd[1]: install_db.service: Failed with result 'exit-code'.
Jul 09 02:55:12 qemux86-64 systemd[1]: Failed to start Install MySQL Community Server Database.

The scripts required by install_db.service are packaged in
mariadb-server which depends on mariadb-setupdb already. So move the
scripts to mariadb-setupdb to make sure start install_db.service
successfully. And move creating user 'mysql' in mariadb-setupdb as well.
Packageconfig 'setupdb' has been useless from last upgrade, so remove it
at same time.

Signed-off-by: Kai Kang <[email protected]>
Signed-off-by: Khem Raj <[email protected]>