AllJOYN-2172 Increased wait time for JoinSession unit test

On some systems the wait time of 1 second was causing the test to fail.
Since there is nothing saying the test must complete in 1 second the wait
time has been increased from 1 second to 5 seconds to prevent false unit
test failures.

Change-Id: Ic6367cd1fcd80cf705c4efdcba2e949efc59d072