Cleaner handling of global_system_variables.wsrep_on

[Nirbhay Choubey]

While going through the code I found that global value of wsrep_on is flipped quite a number of times. This may lead to confusion and bugs.

For instance :

a) In init_common_variables() wsrep_check_opts returns non-zero (error) when say binlog_format=statement.
...
  /* This is a protection against mutually incompatible option values. */
  if (WSREP_ON && wsrep_check_opts (remaining_argc, remaining_argv))
    global_system_variables.wsrep_on= 0;
...

b) Later its back to ON during option handing (default ON).
...
  if (get_options(&remaining_argc, &remaining_argv))
...

c) Then its set again in wsrep_init() based on wsrep_provider's value.

Eventually, the node will be up given a valid provider is specified. But this was not intended according to (a).

[Nirbhay Choubey (nirbhay)]

Step (b) turns it back ON as @@global.wsrep_on is ON by default.