[Profile] Fix fork test and add tests for execlp and execvp after patch...

[Profile] Fix fork test and add tests for execlp and execvp after patch https://reviews.llvm.org/D53593

Summary: This is a follow-up of patch https://reviews.llvm.org/D53593

Reviewers: marco-c

Reviewed By: marco-c

Subscribers: delcypher, llvm-commits, #sanitizers, sylvestre.ledru

Differential Revision: https://reviews.llvm.org/D54167

llvm-svn: 346314