zabbix_agentd: Update to 6.0.19 (LTS)

zabbix_agentd: Update to 6.0.19 (LTS)

- Update from version 6.0.16 to 6.0.19
- Update of rootfile not required

Bugs fixed:
 - ZBX-22798:
   Incorrect output of vfs.file.contents when reading frequently
   modified file
 - ZBX-22470:
   Zabbix Agent locks in tls_recv() when using DebugLevel=5
 - ZBX-21892:
   vfs.fs.get returns wrong data if multiple file systems have identical
   mount point

Full changelogs since 6.0.16:
- https://www.zabbix.com/rn/rn6.0.17
- https://www.zabbix.com/rn/rn6.0.18
- https://www.zabbix.com/rn/rn6.0.19

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>