ISSUE=9529 flow stat cache thread dies

In some circumstances the flow stat cacher thread is dying.  Its
related to a null pointer exception related to getProxy returning null
when the proxy is not found.  I fixed this in several locations.  While
trouble shooting we also found a potential synchronization issue with
the FlowSpaceFirewall.java class this.switches object not being
synchornized
Merge pull request #78 from ajragusa/ISSUE=9529-flow_stat_cache-thread-dies

ISSUE=9529 flow stat cache thread dies