face: Refactored code to set interest filter

Change-Id: I1f9637a79c03a9e24608403d963bbfc4d9bcab1c
diff --git a/src/encoding/block.cpp b/src/encoding/block.cpp
index fbd5838..98c131a 100644
--- a/src/encoding/block.cpp
+++ b/src/encoding/block.cpp
@@ -175,8 +175,8 @@
   , m_type(type)
   , m_begin(m_buffer->end())
   , m_end(m_buffer->end())
-  , m_value_begin(m_buffer->begin())
-  , m_value_end(m_buffer->end())
+  , m_value_begin(value.begin())
+  , m_value_end(value.end())
 {
   m_size = Tlv::sizeOfVarNumber(m_type) + Tlv::sizeOfVarNumber(value_size()) + value_size();
 }