PixelConditionsTool: Reduce calling getCacheEntry
Builds on @emoon's work (!74034 (closed)), before she finished her summer placement:
Mutex lock is required before entering getCacheEntry in getBSErrorWord. getBSErrorWord is called repetitively in a loop calling getCacheEntry. By calling getCacheEntry earlier and passing down, we avoid unnecesary calls to getCacheEntry.
Added a check on retrieving the BSErrorContainer in MC, and added InDetByteStreamErrors to the AthSimulation build.