[LITMUS^RT] Pfair period enforcement fix

[Björn Brandenburg]

Hi everyone,

I've come across a bug in the handling of new tasks in the PFAIR plugin: if there is *no* synchronous release, then the release time of the first job might not be initialized properly, which in turn caused the period parameter to be effectively ignored. I've pushed a fix to prop/pfair-period-fix to resolve this issue.

	https://github.com/LITMUS-RT/litmus-rt/compare/prop;pfair-period-fix

I've also added corresponding tests to liblitmus:

	https://github.com/LITMUS-RT/liblitmus/compare/prop;job-count-test

Unless there are objections, I'll merge the patches in the coming days.

Thanks,
Björn