Remove and rename misleading method

[ekigamba]

• Method org.smartregister.immunization.util.VaccinatorUtils#getVaccineFromVaccineConfigFile method is misleading since it only serves to read special vaccines.
  This method provides a redundant/duplicate cache for vaccines while we have a new cache that was introduced during a refactor.
  The main and only vaccine cache is supposed to be org.smartregister.immunization.ImmunizationLibrary#vaccineCacheMap

TASKS

• Remove this duplicate cache and fix references from this cache in immunization, child & client applications(bangladesh, zeir, BA)
• For backwards compatbility, remove the cache but retain the method(s) and their signatures so that they point to the main cache
• Make sure the special vaccines file is loaded in the main cache