lib-storage: Don't leak memory if mailbox_save_set_flags() is used multiple times for keywords. This affected only some external plugins.
lib-storage: Don't leak memory if mailbox_save_set_flags() is used multiple times for keywords.
This affected only some external plugins.

dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot