Fixed error message logged for certificate verification

Return value of certificate verification failure is validated
for any known errors like certificate not yet valid, self
signed certificate before returning error.

As the message logged before comparing with known errors is
misleading changed the error message and also level of the
log message to INFO.

Tested:
phosphor-certificate-manager[556]: Certificate install
phosphor-certificate-manager[556]: Certificate loadCert
phosphor-certificate-manager[556]: Error occured during X509_verify_cert call,
checking for known error
phosphor-certificate-manager[556]: Certificate compareKeys
phosphor-certificate-manager[556]: Certificate loadCert

"ERROR_STR" : "unable to get local issuer certificate",
"ERRCODE" : "20",

Signed-off-by: Marri Devender Rao <devenrao@in.ibm.com>
Change-Id: I2df9abc766086a9d80063c32ccc8e44b62c48fc1
diff --git a/certificate.cpp b/certificate.cpp
index 51c8ec6..0b4b0ed 100644
--- a/certificate.cpp
+++ b/certificate.cpp
@@ -225,9 +225,11 @@
     else if (errCode == 0)
     {
         errCode = X509_STORE_CTX_get_error(storeCtx.get());
-        log<level::ERR>("Certificate verification failed",
-                        entry("FILE=%s", filePath.c_str()),
-                        entry("ERRCODE=%d", errCode));
+        log<level::INFO>(
+            "Error occured during X509_verify_cert call, checking for known "
+            "error",
+            entry("FILE=%s", filePath.c_str()), entry("ERRCODE=%d", errCode),
+            entry("ERROR_STR=%s", X509_verify_cert_error_string(errCode)));
     }
     else
     {