librc: prevent false daemon matches across files

[pva]

_match_daemon() removes successful matches from the list while looking for a match. rc_service_daemon_set() and rc_service_started_daemon() call it with the same list for each daemon record file they scan. This causes a criterion matched by one file to be no longer required from the next: partial matches from different files could add up to a successful match.

Fix this by matching each file against a private copy of the list.

To reproduce the problem:

export D=/var/tmp/
mkdir -p "$D/openrc/daemons/foo"
printf 'exec=/usr/bin/foo\nargv_0=bar\npidfile=\n' > "$D/openrc/daemons/foo/001"
printf 'exec=/usr/bin/bar\nargv_0=foo\npidfile=\n' > "$D/openrc/daemons/foo/002"
cat >test.c <<EOF
#include <stdio.h>
#include <rc.h>

int main(void)
{
	const char *argv0[] = { "foo", NULL };
	rc_set_user();
	bool r = rc_service_started_daemon("foo", "/usr/bin/foo", argv0, 0);
	printf("%s\n", r ? "true (bug)" : "false");
	return !r;
}
EOF
gcc -o repro test.c -lrc
XDG_RUNTIME_DIR="$D" ./repro

Should not match, but it matches before this patch.