Skip and warn on wonky /etc/os-release lines

If the lines don't split cleanly (occasionally STDERR gets mixed in, for
instance, due to our current SSH output setup), we should simply
log.Warn in the output instead of bailing completely.

Signed-off-by: Nathan LeClaire <nathan.leclaire@gmail.com>

libmachine/provision/os_release.go

@@ -69,7 +69,8 @@ func (osr *OsRelease) ParseOsRelease(osReleaseContents []byte) error {
 	for scanner.Scan() {
 		key, val, err := parseLine(scanner.Text())
 		if err != nil {
-			return err
+			log.Warn("Warning: got an invalid line error parsing /etc/os-release: %s", err)
+			continue
 		}
 		if err := osr.setIfPossible(key, val); err != nil {
 			log.Debug(err)