Revert "High: IPC: Bug cl#5110 - Prevent 100% CPU usage when looking for synchronous replies"

This reverts commit 68cffae876a8257b07dea116e88c8af7c1ff1039 which is no
longer needed now that libqb has been fixed with:

https://github.com/asalkeld/libqb/commit/709b32de434ec157ec2a73153e58ffec186ae660.

Conflicts:
lib/common/ipc.c