Improve error handling when vgdb cannot read process cmd line



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13233 a5019735-40e9-0310-863c-91ae7b9d1cf9
Fix two memory leaks. Spotted by Coverity.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13234 a5019735-40e9-0310-863c-91ae7b9d1cf9