ima: change the default hash algorithm to SHA1 in ima_eventdigest_ng_init()

Replace HASH_ALGO__LAST with HASH_ALGO_SHA1 as the initial value of
the hash algorithm so that the prefix 'sha1:' is added to violation
digests.

Fix commit:
  4d7aeee ima: define new template ima-ng and template fields d-ng and n-ng
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Cc: <stable@vger.kernel.org> # 3.13.x
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/ima_template_lib.c

@@ -251,7 +251,7 @@ int ima_eventdigest_ng_init(struct integrity_iint_cache *iint,
 			    struct evm_ima_xattr_data *xattr_value,
 			    int xattr_len, struct ima_field_data *field_data)
 {
-	u8 *cur_digest = NULL, hash_algo = HASH_ALGO__LAST;
+	u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
 	u32 cur_digestsize = 0;
 
 	/* If iint is NULL, we are recording a violation. */