src/libpcp/src/context.c: reduce chatter from close channel routines
src/libpcp/src/context.c: reduce chatter from close channel routines

When __pmGetPDU returns 0 (pdu type) this means the channel has been
closed remotely ... don't report anything here, just let the PM_ERR_IPC
percolate back up the PMAPI to the client.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp