Consolidate and simplify .gitignore files for certs.

Hopefully, this should avoid issues like 4f60908.

Author: lgarron

certs/.gitignore

@@ -1,2 +1,6 @@
-/gen
-/src/crt/*.srl
+/src/crt/*.srl
+*.key
+sets/current
+sets/*/gen
+sets/*/pregen/crt
+sets/*/pregen/key