Only show Introduction Accept Information if success is still possible

.../briarproject/briar/android/contact/ConversationItem.java

...arproject/briar/api/introduction/IntroductionRequest.java

...rproject/briar/api/introduction/IntroductionResponse.java

...iarproject/briar/introduction/AbstractProtocolEngine.java

.../org/briarproject/briar/introduction/IntroduceeState.java

.../org/briarproject/briar/introduction/IntroducerState.java

...arproject/briar/introduction/IntroductionManagerImpl.java

.../main/java/org/briarproject/briar/introduction/State.java

...oject/briar/introduction/IntroductionIntegrationTest.java