[7.4.z] define units for all values

from support ticket:

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Per the 7.2 configuration guide: https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.2/html-single/configuration_guide/index#reference_of_datasource_statistics Some of the statistics explicitly indicate that they are in milliseconds. What are the units for the other statistics? Seconds/milliseconds/both?

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We should be including units for every value.