WebSearch: webcoll performance improvements

* Introduces new -q/--quick CLI argument that improves webcoll
  performance by skipping the rebuilding of webpage cache
  for collections whose reclist has not been modified within the
  last phase1 run (unless --force or --collection CLI arguments
  were specified).

* Removes a point of sleep that could have lead to potential
  race conditions.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>