link to jjb cache documentation in the handbook .

Additional documentation was added for jjb cache in jjb manual.
Instead of documenting it twice, this
patch simply points to the jjb manual.

Depends on I57cf59c8723aa04e20801f32a81b573c9d096b48
Fixes bug 1193450

Change-Id: I1741d9774540d1e6b877533f29238663c2890028
Merge "link to jjb cache documentation in the handbook ."