Generally the sap hostgent is updated when you update your SAP Kernel as of SAP Hostagent 7.22 PL052, but at many instance we need to manullay upgrade SAP hostagent.
Upgrading SAP Host Agent Without Extracting the SAPHOSTAGENT Archive.
Download the required target release version of the SAPHOSTAGENT<SP-version>
Log in as root user and
/usr/sap/hostctrl/saphostexec -upgrade -archive <path to downloaded SAPHOSTAGENT<SP-version>.SAR>
For more information : https://help.sap.com/doc/saphelp_nw73ehp1/7.31.19/en-US/a9/4798cf6d9f4c0190ecf7144fd05832/content.htm