Double values printed by ipc with shmem to verify readings. IPC to be removed
soon.
No need do update snmp's part of wr_mon since it will be removed (snmp will
use shmem directly).
Include implementation of shmem locks for read.

It was seen that phase setpoint read via shmem sometimes differs from value
read via ipc. However it shmem's value is more recent. Assignment of ipc's
cur_setpoint in ppsi's servo is done before setting to new value.
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>