Fixes for few leaks and improved error handling.

Fixes for few leaks and improved error handling.

Fix a memory leak detected by coverity scan. It is not critical,
but it is real in an error case when there is no end mark. While
fixing it, also enhanced code to handle different error cases
properly because we would want valid content to be decoded even
when there are invalid marks in the log file. Invalid log marks
are possible when vmware.log gets rotated in the middle of guest
logging.

While verifying the fix using valgrind, found a couple of more
leaks in panic and warning stubs. Addressed those as well.