[DOC] Promote high level "reload" operation over the low level ":reload" one

Based on the description in JBEAP-15338, we should promote high-level "reload" CLI operation over the low-level ":reload" one (except for cases where that operation ties with domain-mode server).

Using grep I have found two following occurrences of the low-level ":reload" operation in the doc:

1. Performance tuning guide - 11.1. Monitoring JGroups Statistics
2. Developing EJB Applications - 4.1. Message-Driven Beans

Please replace :reload with just reload so the high-level operation is invoked in these cases.