If the IP address for X2AP is not good, the error message reported
was very unclear. Attempt to make it better.

This commit manually reverts the commits:
- 97c69dc4
- 3278aa49

The basic simulator was not functional anymore because
the UE did not send RRCConnectionSetupComplete due to
some problem in the PDCP layer, most probably.

This break was there and went away, for whatever reason...

The bug popped up when one UE was doing TCP UL iperf and a second UE
attempted to connect. A crash of the eNB happened because we changed
the wrong NFAPI structure in a TTI where both UEs are scheduled.

Something like that.

SCTP: one to many sockets implementation

Fix: RAN API: remove_ul_slice() frees ul sched_name pointer, when sched_name set, free it when resetting

Commit 7823858e introduced this as a comment.

The comparison in AssertFatal was not correct,
taking the opposite meaning to the one expected.

Affects:
* store_dlsch_buffer()
* assign_rbs_required()

When the RLC layer returns error codes (like dropped packets), this is still
counted as PDCP layer traffic. In order to reflect dropped packets or
malfunctioning, this patch makes that upon an RLC error code, the function is
exited immediately. In this case, it is not counted as additional PDCP traffic.

An example is too much UDP traffic. If the RLC buffer is saturated and the
packet therefore refused, incoming traffic won't be counted anymore. With this
patch, the PDCP layer statistics won't count such traffic anymore.

the integration of the nfapi-L2-emulator-for-develop (f254107b) added more
types in the RCconfig_flexran(), but they were partially wrong. This commit
fixes those types after the rebase of this branch on top of 2018.w19

* give the correct UE_id instead an index of the protobuf message (they can
  diverge from each other)
* in the PDCP part of the RAN API, the RAN API has to make the conversion UE_id
  (MAC) to UID (PDCP)
* a follow up commit could clean up the interfaces:
  - the MAC functions take the UE_id
  - the RRC functions take the RNTI
  - the PDCP functions take the UID
  this would mean the caller has to find those ID but would decrease
  computations since the RAN API functions do not have to do that themselves

If the buffer in the RLC is full, testing the buffer state over and over again
slows the DL traffic down. In order to circumvent this, the PDCP will drop any
data during a configurable time (compile-time) before it delivers data to RLC
again.

To change this, see the constant TM_SKIP_FULL_BUF_MS in pdcp.h.