The problem is caused by Tomcat being unable to reach its target cache size due to cache entries that are less than the TTL of those entries.
So Tomcat didn't have enough cache entries that it could expire, because they were too fresh, it couldn't free enough cache and thus outputs warnings.
The problem didn't appear in Tomcat 7 because Tomcat 7 simply didn't output warnings in this situation.
With the upgrade of Tomcat to version 8 Release automation started to log this message as we are using the default cache size.
The maximum of the static resource cache (all resources in total) is by default 10240 kbyte (10 mbyte).
You can increase this by adding the following line to the RA_HOME\conf\context.xml file.
<Resources cachingAllowed="true" cacheMaxSize="100000" />
At the end of the file just before the
This will increase the cache size to 100Mb.
You need to restart the Release automation Tomcat service.