Replace heap allocation with stack allocation

The key_entry in spki_table_remove_entry() is now placed on the stack.
Fix memory leak in spki_table_search_by_ski()
Replace write-lock with read-lock in spki_table_search_by_ski()
Fix memory leak and replace write-lock with read-lock

spki_table_get_all()
	Replace write-lock with read-lock
	Fix memory leak
	Simplify key_entry_to_spki_record() call