I believe that is part of the hp agentless management service (daemon hp-ams). More info about hp-ams can be found here: HP Blogs - HP ProLiant Gen8 Agentless Management Overview - The HP Blog Hub
hp-ams needs to connect to ESXi in order to get some HW/SW info, and it does under the root credential, which is by default logged by ESXi. To make sure it is hp-ams causing it, you can stop it and watch Events and verify they stopped. To stop hp-ams you can run /etc/init.d/hp-ams.sh stop and then /etc/init.d/hp-ams.sh start . More info about these commands on http://h20000.www2.hp.com/bc/docs/support/SupportManual/c03306157/c03306157.pdf
However, I cannot say the number of times it is connecting per minute is normal or not, sorry about this.
Hope that helps a little.
Regards,