Long lines are harder to read and harder to diff; in fact, if lines get
too long (> 1000 bytes), it starts causing issues where git send-email
refuses to send patches for the file.  I've cleaned up the tests
directory in the past (see commits bd6c46fa, 3b750d13), but new long
lines have been introduced in the meantime.

Why 90 instead of 80? Because there were too many tests on the fringe
edge, and I didn't want to edit that many files.

Add a syntax check to prevent future long lines.

* cfg.mk (sc_prohibit_long_lines): New rule.
* tests/qemuxml2argvdata/qemuxml2argv-*.args: Split lines of any
file with content longer than 90 columns.
* tests/storagevolxml2argvdata/*.argv: Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

A better way to do this would be to use a configuration file like

   [iscsi "target-name"]
   user = name
   password = pwd

and pass it via -readconfig.  This would remove the username and password
from the "ps" output.  For now, however, keep this solution.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

libiscsi provides a userspace iSCSI initiator.

The main advantage over the kernel initiator is that it is very
easy to provide different initiator names for VMs on the same host.
Thus libiscsi supports usage of persistent reservations in the VM,
which otherwise would only be possible with NPIV.

libiscsi uses "iscsi" as the scheme, not "iscsi+tcp".  We can change
this in the tests (while remaining backwards-compatible manner, because
QEMU uses TCP as the default transport for both Gluster and NBD).
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>