web: Don't warn about D-Bus signals without proxies

We get them now since "dbus-json: Allow working without D-Bus
proxies".

Closes #752
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Spell it "host name" instead of "hostname"

Fixes #738
Closes #762
Reviewed-by: Stef Walter <stefw@redhat.com>
cockpit: All processes and  tests ignore SIGPIPE.

Make sure all processes and tests (except for some testing mock processes) ignore SIGPIPE.
Replace g_test_init() with cockpit_test_init() in the main of test-machines.

Fixes #716
Merge branch 'master' of https://github.com/cockpit-project/cockpit into yin/http