CLEANUP: ssl_ckch: Use corresponding enum for commit_cacrlfile_ctx.cafile_type

There is an enum to determine the entry entry type when changes are
committed on a CA/CRL entry. So use it in the service context instead of an
integer.

This patch may help to fix issue #1731.
diff --git a/src/ssl_ckch.c b/src/ssl_ckch.c
index ccd02ff..899eaa6 100644
--- a/src/ssl_ckch.c
+++ b/src/ssl_ckch.c
@@ -126,7 +126,7 @@
 	struct cafile_entry *new_crlfile_entry;
 	struct ckch_inst_link *next_ckchi_link;
 	struct ckch_inst *next_ckchi;
-	int cafile_type; /* either CA or CRL, depending on the current command */
+	enum cafile_type cafile_type; /* either CA or CRL, depending on the current command */
 	char *err;
 	enum {
 		CACRL_ST_INIT = 0,