Fix printing of cache age metric
Fix printing of cache age metric

Use of echo can differ across platforms, printf is more portable.

maier/nad,circonus-labs/nad,maier/nad,maier/nad,circonus-labs/nad,maier/nad,circonus-labs/nad,circonus-labs/nad,maier/nad,maier/nad,circonus-labs/nad,circonus-labs/nad