Add getter for defaultKeepEvents

[antobinary]

Follow up to #11681

I am adding a getter for defaultKeepEvents

In some environments I see

2021-03-21T19:54:50.686-04:00 ERROR o.s.boot.SpringApplication - Application startup failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'meetingService' defined in class path resource [spring/resources.xml]: Cannot resolve reference to bean 'paramsProcessorUtil' while setting bean property 'paramsProcessorUtil'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'paramsProcessorUtil' defined in class path resource [spring/resources.xml]: Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyException: Invalid property 'defaultKeepEvents' of bean class [org.bigbluebutton.api.ParamsProcessorUtil]: Bean property 'defaultKeepEvents' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?