Return false on socket read error

FrameworkListener was returning the errno from a function marked as
returning bool which caused an implicit conversion to true since we were
in an error block where errno was set to something non-zero.

This caused the clients that had errors to stick around forever and not
get removed from the set of file descriptors that SocketListener was
listening to.

Change-Id: Ia27a4cac47459f3a3c2bb6a7f66803a3165c894a