Coverity analysis defect 11083: Data race condition (MISSING_LOCK)

A new defect has been detected and assigned to mattd@10gen.com in Coverity Connect http://coverity.mongodb.com//sourcebrowser.htm?projectId=10001#mergedDefectId=11083
The defect was flagged by checker MISSING_LOCK in
file /src/mongo/shell/dbshell.cpp
function quitNicely(int)
and this ticket was created by matt.kangas@10gen.com