Fix several Coverity CIDs in devd

CID 1362055, 1362054: File descriptor leaks during shutdown
CID 1362013: Potential null-termination fail with long network device names
CID 1362097: Uncaught exception during memory pressure
CID 1362017, 1362016: Unchecked errors, possibly resulting in weird behavior
if two devd instances start at the same time.
CID 1362015: Unchecked error that will probably never fail

Reported by: Coverity
CID: 1362055 1362054 1362013 1362097 1362017 1362016 1362015
MFC after: 4 weeks
Sponsored by: Spectra Logic Corp