This method finds a parent for orphan for the specified stripe by searching
randomly in the "Spare Capacity Group" (this terminology is borrowed from the
SplitStream implementation, but in this implementation, the Spare Capacity Group is
nothing more than a Set of nodes having spare outbound bandwidth enough to handle
one more child.
Constructs a new exception with the specified cause and a detail message of (cause==null
? null : cause.toString()) (which typically contains the class and detail message of
cause).
Constructs a new exception with the specified cause and a detail message of (cause==null
? null : cause.toString()) (which typically contains the class and detail message of
cause).