ifindex_alloc_locked() never fails and doesn't have no-lock version,
so change the prototype.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
MFV r274271:

Improve zdb -b performance:

 - Reduce gethrtime() call to 1/100th of blkptr's;
 - Skip manipulating the size-ordered tree;
 - Issue more (10, previously 3) async reads;
 - Use lighter weight testing in traverse_visitbp();

Illumos issue:
    5243 zdb -b could be much faster

MFC after:	2 weeks
ctld(8) doesn't require -lcam or -lssl; remove those from DPADD and LDADD.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Improve wording in ctl.conf(5).

Differential Revision:	https://reviews.freebsd.org/D1020
Reviewed by:	bcr@ (earlier version), wblock@
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation