implement session stat command

Implement the session stat command.

Change-Id: I1ff715dd32d963722182db84b475bc9adbfcc7ea
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/ipmiblob/test/blob_interface_mock.hpp b/src/ipmiblob/test/blob_interface_mock.hpp
index 97f37df..0faa6fe 100644
--- a/src/ipmiblob/test/blob_interface_mock.hpp
+++ b/src/ipmiblob/test/blob_interface_mock.hpp
@@ -15,6 +15,7 @@
                                   const std::vector<std::uint8_t>&));
     MOCK_METHOD0(getBlobList, std::vector<std::string>());
     MOCK_METHOD1(getStat, StatResponse(const std::string&));
+    MOCK_METHOD1(getStat, StatResponse(std::uint16_t));
     MOCK_METHOD2(openBlob, std::uint16_t(const std::string&, std::uint16_t));
     MOCK_METHOD1(closeBlob, void(std::uint16_t));
     MOCK_METHOD3(readBytes,