libqos: Track QTestState with QPCIBus

When initializing a QPCIBus, track which QTestState the bus is
associated with (so that a later patch can then explicitly use
that test state for all communication on the bus, rather than
blindly relying on global_qtest).  Update the initialization
functions to take another parameter, and update all callers to
pass in state (for now, most callers get away with passing the
current global_qtest as the current state, although this required
fixing the order of initialization to ensure qtest_start() is
called before qpci_init*() in rtl8139-test, and provided an
opportunity to pass in the allocator in e1000e-test).

Touch up some allocations to use g_new0() rather than g_malloc()
while in the area, and simplify some code (all implementations
of QOSOps provide a .init_allocator() that never fails).

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
[thuth: Removed hunk from vhost-user-test.c that is not required anymore,
 fixed conflict in qtest_vboot() and adjusted qpci_init_pc() in sdhci-test]
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/tests/e1000e-test.c b/tests/e1000e-test.c
index c612dc6..d8085d9 100644
--- a/tests/e1000e-test.c
+++ b/tests/e1000e-test.c
@@ -392,12 +392,12 @@
     qtest_start(cmdline);
     g_free(cmdline);
 
-    test_bus = qpci_init_pc(NULL);
-    g_assert_nonnull(test_bus);
-
     test_alloc = pc_alloc_init();
     g_assert_nonnull(test_alloc);
 
+    test_bus = qpci_init_pc(global_qtest, test_alloc);
+    g_assert_nonnull(test_bus);
+
     e1000e_device_init(test_bus, d);
 }