scylla_raid_setup: revert workaround patch and stop using mdmonitor

We found that monitor mode of mdadm does not work on RAID0, and it is
not a bug, expected behavior according to RHEL developer.
Therefore, we should revert workaround patch which downgrades mdadm,
and stop enabling mdmonitor since we always use RAID0.

See #9540

Closes #10077

dist/common/scripts/scylla_raid_setup

@@ -115,11 +115,6 @@ if __name__ == '__main__':
         pkg_install('xfsprogs')
     if not shutil.which('mdadm'):
         pkg_install('mdadm')
-    if args.raid_level != '0':
-        try:
-            md_service = systemd_unit('mdmonitor.service')
-        except SystemdException:
-            md_service = systemd_unit('mdadm.service')
 
     print('Creating {type} for scylla using {nr_disk} disk(s): {disks}'.format(type='RAID0' if raid else 'XFS volume', nr_disk=len(disks), disks=args.disks))
     procs=[]
@@ -154,16 +149,11 @@ if __name__ == '__main__':
     os.makedirs(mount_at, exist_ok=True)
 
     uuid = run(f'blkid -s UUID -o value {fsdev}', shell=True, check=True, capture_output=True, encoding='utf-8').stdout.strip()
-    after = 'local-fs.target'
-    wants = ''
-    if raid and args.raid_level != '0':
-        after += f' {md_service}'
-        wants = f'\nWants={md_service}'
     unit_data = f'''
 [Unit]
 Description=Scylla data directory
 Before=scylla-server.service
-After={after}{wants}
+After=local-fs.target
 DefaultDependencies=no
 
 [Mount]
@@ -187,8 +177,6 @@ WantedBy=multi-user.target
             f.write(f'RequiresMountsFor={mount_at}\n')
 
     systemd_unit.reload()
-    if args.raid_level != '0':
-        md_service.start()
     mount = systemd_unit(mntunit_bn)
     mount.start()
     if args.enable_on_nextboot: