[fs][metrics]: GetAttr scale.

GetAttr is a set of memory reads, this should be in nanoseconds.

TEST=CQ

Change-Id: I984b00f59c22b1f7e113a927277b334be48ac10d
diff --git a/system/ulib/fs/metrics.cpp b/system/ulib/fs/metrics.cpp
index e8f511d..0286179 100644
--- a/system/ulib/fs/metrics.cpp
+++ b/system/ulib/fs/metrics.cpp
@@ -126,7 +126,7 @@
     set_attr.Initialize(MakeHistogramOptions(micro_base, VnodeCobalt::MetricId::kSetAttr,
                                              VnodeCobalt::EventCode::kUnknown),
                         collector);
-    get_attr.Initialize(MakeHistogramOptions(micro_base, VnodeCobalt::MetricId::kGetAttr,
+    get_attr.Initialize(MakeHistogramOptions(nano_base, VnodeCobalt::MetricId::kGetAttr,
                                              VnodeCobalt::EventCode::kUnknown),
                         collector);
     sync.Initialize(MakeHistogramOptions(micro_base, VnodeCobalt::MetricId::kSync,