use namespace for ca and rename CaState to ca::RequestState

Change-Id: I2250bf7fb68503465dae18e16dc3c512fe809037
diff --git a/src/detail/challenge-encoder.cpp b/src/detail/challenge-encoder.cpp
index dfe76ad..f3ebb5a 100644
--- a/src/detail/challenge-encoder.cpp
+++ b/src/detail/challenge-encoder.cpp
@@ -24,7 +24,7 @@
 namespace ndncert {
 
 Block
-ChallengeEncoder::encodeDataContent(const CaState& request)
+ChallengeEncoder::encodeDataContent(const ca::RequestState& request)
 {
   Block response = makeEmptyBlock(tlv::EncryptedPayload);
   response.push_back(makeNonNegativeIntegerBlock(tlv::Status, static_cast<size_t>(request.m_status)));