Fixed some leaks in klee-replay

[ccadar]

Summary:

These fixes some leaks in klee-replay reported in #1512.
While these particular leaks are not important, we should get to a stage where LSan & ASan runs pass.

Checklist:

• The PR addresses a single issue. If it can be divided into multiple independent PRs, please do so.
• The PR is divided into a logical sequence of commits OR a single commit is sufficient.
• There are no unnecessary commits (e.g. commits fixing issues in a previous commit in the same PR).
• Each commit has a meaningful message documenting what it does.
• All messages added to the codebase, all comments, as well as commit messages are spellchecked.
• The code is commented OR not applicable/necessary.
• The patch is formatted via clang-format OR not applicable (if explicitly overridden leave unchecked and explain).
• There are test cases for the code you added or modified OR no such test cases are required.

[ccadar]

Coverage upload fails for some reason, but those are not required checks.

[MartinNowack]

@ccadar Can you remove the line in: https://github.com/klee/klee/blob/master/utils/sanitizers/lsan.txt to not ignore this leak anymore?

[ccadar]

@MartinNowack Unfortunately, there is still one leak remaining in there, which is uglier to fix. So we can't remove that line in this PR...

[MartinNowack]

Ok, let's merge this for now and try to fix the remaining issues in a later PR. Thanks @ccadar