ssa.c: Code Refactoring.

 Rename UPSTREAM_TIMER_SLOT -> UPSTREAM_RECONNECT_TIMER_SLOT
ssa.c: Code Refactoring.

 Add fd value to log message in case of timerfd_create failure.
ssa.c: Code Refactoring.

 Use define rather than number for upstream fds number.
ssa.c: Code Refactoring.

 Init upstream fds.
Add join timer