pua_reginfo: avoid sending notify when processing location record action triggered by itself

(cherry picked from commit e070257321853d799a6325ac5e94f69b4ccb85e7)
htable: use mode everywhere to control the locks for add operation

(cherry picked from commit c7ff8a88e773e8d25958f86d178f05ee10fd0410)
htable: make locking to access a slot re-entrant for a process

- proper functionality for sht_lock()/sht_unlock()

(cherry picked from commit 4f07daab9cb95e13c7c89a9a566d4a8c88b9145e)
htable: elaborated docs about sht_lock() and sht_unlock()

(cherry picked from commit 44269cd654a6ab0557ca242f25ec41158e7dcbaf)
tm: handle BRANCH_FAILURE_ROUTE in t_check_trans() test

(cherry picked from commit 08248bae17024246442046376a4350007a100025)
pkg/rpm: set version 4.2.1 in spec files
pkg/deb: version set to 4.2.1 in spec files
Makefile.defs: version set to 4.2.1
ChangeLog: content updated for v4.2.1