RFR 4613913: Four EventRequest methods are invokable on deleted request

[Daniil Titov]

Please review the changes that ensure that no operation on deleted com.sun.jdi.request.EventRequest objects are permitted as per JDI specification for com.sun.jdi.request.EventRequestManager.deleteEventRequest(com.sun.jdi.request.EventRequest) method.  The fix makes the following 4 methods in class com.sun.tools.jdi. EventRequestManagerImpl$EventRequestImpl to throw com.sun.jdi.request.InvalidRequestStateException if the request is deleted:
  - getProperty()
  - putProperty(Object, Object)
  - suspendPolicy()
  - isEnabled()

Bug: https://bugs.openjdk.java.net/browse/JDK-4613913
Webrev: http://cr.openjdk.java.net/~dtitov/4613913/webrev.02/

Best regards,
Daniil