When a member in Group Replication is faced to a error it does the
following steps:
 1) changes its state to ERROR;
 2) leave the group;
 3) on network failures will attempt to rejoin;
 4) follows group_replication_exit_state_action.
While new features were added, several implementations of these
steps were introduced, which led to code duplication.

This patch does merge all these implementations into a single one.
Also it obsoletes two error messages that are no more used.

ReviewBoard: 22283