This is very easy to overlook because the attribute is extremely poorly named and missing from MCMP definition [1] completely. This is because mod_cluster aligned nomenclature with httpd mod_proxy's [2] which defines maxattempts as:

Maximum number of failover attempts before giving up.

and not total number attempts. This means, that value od 0 is a valid value meaning no retry.

[1] https://developer.jboss.org/docs/DOC-11425

[2] https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypass