Do not compile ChronoSync support by default

ChronoSync dependency is now made optional
and is kept for testing purposes only.

Also change sig-type to ecdsa-sha256 in nlsr.conf
as ndn-cxx now has strict checking for it.

refs: #5147

Change-Id: I95c9fb844681ebf2c4e7bbb03cc7796a0795de83
diff --git a/src/conf-parameter.cpp b/src/conf-parameter.cpp
index 47a33e8..fb92aa2 100644
--- a/src/conf-parameter.cpp
+++ b/src/conf-parameter.cpp
@@ -26,7 +26,7 @@
 INIT_LOGGER(ConfParameter);
 
 // To be changed when breaking changes are made to sync
-const uint64_t ConfParameter::SYNC_VERSION = 9;
+const uint64_t ConfParameter::SYNC_VERSION = 10;
 
 static std::unique_ptr<ndn::security::CertificateFetcherDirectFetch>
 makeCertificateFetcher(ndn::Face& face)
@@ -52,7 +52,7 @@
   , m_corR(0)
   , m_maxFacesPerPrefix(MAX_FACES_PER_PREFIX_MIN)
   , m_syncInterestLifetime(ndn::time::milliseconds(SYNC_INTEREST_LIFETIME_DEFAULT))
-  , m_syncProtocol(SYNC_PROTOCOL_CHRONOSYNC)
+  , m_syncProtocol(SYNC_PROTOCOL_PSYNC)
   , m_adjl()
   , m_npl()
   , m_validator(makeCertificateFetcher(face))