Fix some serious bugs in the way memcache was being used.  We were caching None values, because the value to be cached was computed *after* the memcache.add() call.  This was in the code ever since the use of memcache was introduced here, so it was never effective.  I also simplified the lookup in memcache_results to memcache_results.get(email), and decided to set the timeout to 5 minutes for all emails.  Most emails without nicknames will never actually get one assigned, because they are e.g. mailing lists or aliases for users who do their review under a different account.
Fix some serious bugs in the way memcache was being used.  We were
caching None values, because the value to be cached was computed
*after* the memcache.add() call.  This was in the code ever since the
use of memcache was introduced here, so it was never effective.  I
also simplified the lookup in memcache_results to
memcache_results.get(email), and decided to set the timeout to 5
minutes for all emails.  Most emails without nicknames will never
actually get one assigned, because they are e.g. mailing lists or
aliases for users who do their review under a different account.

I think this may obviate the need for the entity caching that Brad is
experimenting with in issue 2944.  I do notice that each Account is
loaded three times on a cache miss; but we should have many fewer
cache misses now...

gavioto/rietveld,openlabs/cr.openlabs.co.in,nbodepallictr/touchites-test,nbodepallictr/touchites-codereview,sajingeo/rietveld,arg0/rietveld,salomon1184/rietveld,google-code-export/rietveld,nareshboddepalli/touchites-test,openlabs/cr.openlabs.co.in,supriyantomaftuh/rietveld,rietveld-codereview/rietveld,nareshboddepalli/touchites-test,kscharding/integral-solutions-smxq,google-code-export/rietveld,draem0507/rietveld,v3ss0n/rietveld,sajingeo/rietveld,dushmis/rietveld,Koulio/rietveld,gavioto/rietveld,gco/rietveld,andyzsf/rietveld,fuzan/rietveld,ericmckean/rietveld,andyzsf/rietveld,dushmis/rietveld,berkus/rietveld,fuzan/rietveld,xtypebee/rietveld,nareshboddepalli/touchites-codereview,openlabs/cr.openlabs.co.in,gavioto/rietveld,aungzanbaw/rietveld,robfig/rietveld,robfig/rietveld,arg0/rietveld,sajingeo/rietveld,DeanHere/rietveld,ericmckean/rietveld,aungzanbaw/rietveld,aungzanbaw/rietveld,nbodepallictr/touchites-codereview,google-code-export/rietveld,DeanHere/rietveld,fuzan/rietveld,rietveld-codereview/rietveld,berkus/rietveld,foolonhill/rietveld,nareshboddepalli/touchites-codereview,rietveld-codereview/rietveld,kscharding/integral-solutions-smxq,foolonhill/rietveld,nareshboddepalli/touchites-codereview,andyzsf/rietveld,robfig/rietveld,salomon1184/rietveld,nbodepallictr/touchites-test,dushmis/rietveld,gco/rietveld,berkus/rietveld,kscharding/integral-solutions-smxq,v3ss0n/rietveld,Koulio/rietveld,supriyantomaftuh/rietveld,rietveld-codereview/rietveld,draem0507/rietveld,DeanHere/rietveld,salomon1184/rietveld,nbodepallictr/touchites-test,gco/rietveld,xtypebee/rietveld,xtypebee/rietveld,draem0507/rietveld,v3ss0n/rietveld,foolonhill/rietveld,Koulio/rietveld,ericmckean/rietveld,nbodepallictr/touchites-codereview,supriyantomaftuh/rietveld,nareshboddepalli/touchites-test,arg0/rietveld