security: apparmor: load the storage driver dynamically

In commit 5e515b54 I've attempted to fix the inability to access
storage from the apparmor helper program by linking with the storage
driver. By linking with the .so the linker complains that it's not
portable. Fix this by loading the module dynamically as we are supposed
to do.
Reviewed-by: NDaniel P. Berrange <berrange@redhat.com>

src/Makefile.am

@@ -3124,7 +3124,7 @@ virt_aa_helper_LDADD =						\
 		libvirt.la					\
 		libvirt_conf.la					\
 		libvirt_util.la					\
-		libvirt_driver_storage.la			\
+		libvirt_driver_storage_impl.la			\
 		../gnulib/lib/libgnu.la
 if WITH_DTRACE_PROBES
 virt_aa_helper_LDADD += libvirt_probes.lo

src/security/virt-aa-helper.c

@@ -41,6 +41,7 @@
 #include "viralloc.h"
 #include "vircommand.h"
 #include "virlog.h"
+#include "driver.h"
 
 #include "security_driver.h"
 #include "security_apparmor.h"
@@ -56,7 +57,6 @@
 #include "virgettext.h"
 
 #include "storage/storage_source.h"
-#include "storage/storage_backend.h"
 
 #define VIR_FROM_THIS VIR_FROM_SECURITY
 
@@ -927,10 +927,10 @@ get_files(vahControl * ctl)
         goto cleanup;
     }
 
-    if (virStorageBackendDriversRegister(false) < 0) {
-        vah_error(ctl, 0, _("failed to register storage driver backend"));
-        goto cleanup;
-    }
+    /* load the storage driver so that backing store can be accessed */
+#ifdef WITH_STORAGE
+    virDriverLoadModule("storage", "storageRegister");
+#endif
 
     for (i = 0; i < ctl->def->ndisks; i++) {
         virDomainDiskDefPtr disk = ctl->def->disks[i];