drvAsynPowerPMACPort.cpp: do not connectIt in readIt()

The typical dialog with the PMAC is done in lowLevelWriteRead(),
first a write() and then a read().

When the connection is established between the write() and the read(),
the write() did fail, and nothing had been send out.
As a consequence, the read() on the newly opened connection will fail as well
with a timeout, since the PMAC had never received anything and will not answer
anything either.

The perfectly working connection will be closed and a new one established.

Avoid this by only (auto)connecting in writeIt().
Call powerPmacAxis::getAxisInitialStatus() when PMAC is connected

The current implementatation does an initial getAxisInitialStatus()
when the axis is created.
This does not work when the PMAC is not connected, the init status
will be undefined.
As another side effect the startup of the IOC is delayed with the timeout
for a TCP connection (which is typically 60 seconds or so)

Solution:
Get the initial status as soon as we have a connection.
Keep track about the connection status in oldAsynStatus_

Note:
A similar change needs to be done in powerPmacCSAxis.cpp