Multiscript: adjusted result object for sequential execution.

TODO

src/lib-sieve/cmd-keep.c

src/lib-sieve/sieve-actions.c

src/lib-sieve/sieve-result.c

src/lib-sieve/sieve-result.h

src/testsuite/tst-test-result.c

tests/execute/actions.svtest

tests/extensions/vacation/execute.svtest