fix typo

fix typo for tools/dstat.sh
retreive must be retrieve

Change-Id: I7a817ec02e7156c886d7d6abb28688bfe2ef5998
diff --git a/tools/dstat.sh b/tools/dstat.sh
index 1c80fb7..ae7306e 100755
--- a/tools/dstat.sh
+++ b/tools/dstat.sh
@@ -9,7 +9,7 @@
 # Assumes:
 #  - dstat command is installed
 
-# Retreive log directory as argument from calling script.
+# Retrieve log directory as argument from calling script.
 LOGDIR=$1
 
 # Command line arguments for primary DStat process.