A thread pool with min size 1 uses only 1 thread for processing

If a thread pool is configured like below

 org.apache.sling.commons.threads.impl.DefaultThreadPool.factory-oak
    name="oak"
    minPoolSize=I"1"
    maxPoolSize=I"5"

Then only 1 thread would be used even if multiple jobs are assigned to the pool. This happens because of strange behaviour of Java ThreadPoolExecutor

If there are more than corePoolSize but less than maximumPoolSize threads running, a new thread will be created only if the queue is full

With unbounded queue used this lead to current behaviour. As a fix Sling Thread Pool should adapt such a config