HPCC-9304 Add PID into Process/eclagent entries of ECL WU xml

Existing ECL WU xml contains only one agentPID. EclWatch uses the
agentPID to identify the log lines for the workunit from eclagent
log. When a WU runs on two different eclagents, EclWatch can only
find out the log lines in one eclagent log using the agentPID. In
this fix, the agentPID of each eclagent is added into the /Process/
/EclAgent/eclagent/ entry of the WU xml. EclWatch uses the agentPID
and the log name to read WU log lines from each eclagent log.

Signed-off-by: Kevin Wang <kevin.wang@lexisnexis.com>