NewProvisioningSession expects pkcs8 private key and SHA race fix

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Fix SHA hashing to remove race condition. This change
fixes the implementation by passing in the digest buffer.

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The input to ProvisioningEngine::NewProvisioningSession should be
pkcs8 private key instead of pkcs1 private key

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=151273394

Change-Id: Ibcdff7757b2ac2878ee8b1b88365083964bfa10a

common/BUILD

@@ -132,6 +132,7 @@ cc_library(
     srcs = ["sha_util.cc"],
     hdrs = ["sha_util.h"],
     deps = [
+        "//base",
         "//external:openssl",
     ],
 )