Make sinsp open methods virtual for tests

Some automated tests might want to subclass sinsp and override the
open() methods in tests. The old single open() method was virtual but
the replacements were not.

This makes them virtual again.

Signed-off-by: Mark Stemm <mark.stemm@gmail.com>

userspace/libsinsp/sinsp.h

@@ -219,15 +219,15 @@ class SINSP_PUBLIC sinsp : public capture_stats_source, public wmi_handle_source
 
 
 	/* Wrappers to open a specific engine. */
-	void open_kmod(unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
-	void open_bpf(const std::string &bpf_path, unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
-	void open_udig();
-	void open_nodriver();
-	void open_savefile(const std::string &filename, int fd = 0);
-	void open_plugin(const std::string &plugin_name, const std::string &plugin_open_params);
-	void open_gvisor(const std::string &config_path, const std::string &root_path);
-	void open_modern_bpf(unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
-	void open_test_input(scap_test_input_data *data);
+	virtual void open_kmod(unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
+	virtual void open_bpf(const std::string &bpf_path, unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
+	virtual void open_udig();
+	virtual void open_nodriver();
+	virtual void open_savefile(const std::string &filename, int fd = 0);
+	virtual void open_plugin(const std::string &plugin_name, const std::string &plugin_open_params);
+	virtual void open_gvisor(const std::string &config_path, const std::string &root_path);
+	virtual void open_modern_bpf(unsigned long driver_buffer_bytes_dim = DEFAULT_DRIVER_BUFFER_BYTES_DIM, const std::unordered_set<uint32_t> &ppm_sc_of_interest = {}, const std::unordered_set<uint32_t> &tp_of_interest = {});
+	virtual void open_test_input(scap_test_input_data *data);
 
 	scap_open_args factory_open_args(const char* engine_name, scap_mode_t scap_mode);