Trivial typo fixes and code refactorings (#5191)

Trivial typo fixes and code refactorings (#5191)

* logind: trivial simplification

free_and_strdup() handles NULL arg, so make use of that.

* boot: fix two typos

* pid1: rewrite check in ignore_proc() to not check condition twice

It's harmless, but it seems nicer to evaluate a condition just a single time.

* core/execute: reformat exec_context_named_iofds() for legibility

* core/execute.c: check asprintf return value in the usual fashion

This is unlikely to fail, but we cannot rely on asprintf return value
on failure, so let's just be correct here.

CID #1368227.

* core/timer: use (void)

CID #1368234.

* journal-file: check asprintf return value in the usual fashion

This is unlikely to fail, but we cannot rely on asprintf return value
on failure, so let's just be correct here.

CID #1368236.

* shared/cgroup-show: use (void)

CID #1368243.

* cryptsetup: do not return uninitialized value on error

CID #1368416.