Use install(1) where possible

This eliminated a number of sudo calls by doing the copy/chown/chmod in
a single step and sets a common pattern.

Change-Id: I9c8f48854d5bc443cc187df0948c28b82c4d2838
diff --git a/lib/sahara b/lib/sahara
index 521b19a..f389326 100644
--- a/lib/sahara
+++ b/lib/sahara
@@ -101,11 +101,7 @@
 
 # configure_sahara() - Set config files, create data dirs, etc
 function configure_sahara {
-
-    if [[ ! -d $SAHARA_CONF_DIR ]]; then
-        sudo mkdir -p $SAHARA_CONF_DIR
-    fi
-    sudo chown $STACK_USER $SAHARA_CONF_DIR
+    sudo install -d -o $STACK_USER $SAHARA_CONF_DIR
 
     if [[ -f $SAHARA_DIR/etc/sahara/policy.json ]]; then
         cp -p $SAHARA_DIR/etc/sahara/policy.json $SAHARA_CONF_DIR
@@ -115,9 +111,7 @@
     cp $SAHARA_DIR/etc/sahara/sahara.conf.sample $SAHARA_CONF_FILE
 
     # Create auth cache dir
-    sudo mkdir -p $SAHARA_AUTH_CACHE_DIR
-    sudo chown $STACK_USER $SAHARA_AUTH_CACHE_DIR
-    sudo chmod 700 $SAHARA_AUTH_CACHE_DIR
+    sudo install -d -o $STACK_USER -m 700 $SAHARA_AUTH_CACHE_DIR
     rm -rf $SAHARA_AUTH_CACHE_DIR/*
 
     configure_auth_token_middleware $SAHARA_CONF_FILE sahara $SAHARA_AUTH_CACHE_DIR