[3919] Added sname_ and file_ initialization

src/lib/dhcp/pkt4.cc

@@ -81,6 +81,9 @@ Pkt4::Pkt4(const uint8_t* data, size_t len)
 
     data_.resize(len);
     memcpy(&data_[0], data, len);
+
+    memset(sname_, 0, MAX_SNAME_LEN);
+    memset(file_, 0, MAX_FILE_LEN);
 }
 
 size_t