* qemud/conf.c: Re-factor bits of conf.c so that:
- qemudMakeConfigPath() can be re-used given another configDir
- split qemudEnsureConfigDir() out of qemudSaveConfig() so
that it may be re-used to create another configDir
- split qemudScanConfigDir() out so that qemudScanConfigs()
can scan multiple configDirs
* qemud/conf.c: handle an unspecified MAC address,
fix the argv freeing code in qemudBuildCommandLine()
and fix copy and paste error in qemudGenerateXML()