doveadm-sieve: Fixed problem with synchronizing the active script.

src/lib-sieve/sieve-script.c

src/lib-sieve/sieve-storage-private.h

src/lib-sieve/sieve-storage-sync.c

src/lib-sieve/sieve-storage.c

src/plugins/doveadm-sieve/doveadm-sieve-plugin.c