lib-sieve: sieve - Use int for sieve_init() status result

src/lib-sieve-tool/sieve-tool.c

src/lib-sieve/sieve.c

src/lib-sieve/sieve.h

src/managesieve/managesieve-capabilities.c

src/managesieve/managesieve-client.c

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

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

src/plugins/imap-filter-sieve/imap-filter-sieve.c

src/plugins/imapsieve/imap-sieve.c

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