Using bootable if set for disk

If nailgun will send as bootable flag for disk we have to use this
disk and place '/boot' on it

Change-Id: I881d9fd4bb378dec78fd86aff0c314c910525110
Closes-bug: 1567450

fuel_agent/drivers/nailgun.py

@@ -137,6 +137,10 @@ class Nailgun(BaseDataDriver):
 
     @property
     def boot_disks(self):
+        """Property to get suitable list of disks to place '/boot'
+
+        :returns: list of disk where boot partition can be placed
+        """
         # FIXME(agordeev): NVMe drives should be skipped as
         # accessing such drives during the boot typically
         # requires using UEFI which is still not supported
@@ -163,9 +167,19 @@ class Nailgun(BaseDataDriver):
         md_boot_disks = [
             disk for disk in self.md_os_disks if disk in suitable_disks]
         if md_boot_disks:
-            return md_boot_disks
+            disks = md_boot_disks
         else:
-            return suitable_disks
+            disks = suitable_disks
+        bootable_disk = [disk for disk in disks
+                         if disk.get('bootable')]
+        if bootable_disk:
+            if len(bootable_disk) >= 2:
+                raise errors.WrongPartitionSchemeError(
+                    "More than one bootable disk found! %{0}".
+                    format(bootable_disk))
+            return bootable_disk
+
+        return disks
 
     def _have_boot_partition(self, disks):
         return any(self._is_boot_disk(d) for d in disks)

fuel_agent/tests/test_nailgun.py

@@ -1757,6 +1757,15 @@ class TestNailgunMockedMeta(unittest2.TestCase):
             drv.partition_scheme.fs_by_mount('/boot').device,
             '/dev/sda3')
 
+    def test_boot_partition_bootable_flag(self, mock_lbd, mock_image_meta):
+        data = copy.deepcopy(PROVISION_SAMPLE_DATA)
+        data['ks_meta']['pm_data']['ks_spaces'][1]['bootable'] = True
+        mock_lbd.return_value = LIST_BLOCK_DEVICES_SAMPLE
+        drv = nailgun.Nailgun(data)
+        self.assertEqual(
+            drv.partition_scheme.fs_by_mount('/boot').device,
+            '/dev/sdb3')
+
     def test_elevate_keep_data_single_disk(self, mock_lbd, mock_image_meta):
         data = copy.deepcopy(PROVISION_SAMPLE_DATA)
         data['ks_meta']['pm_data']['ks_spaces'] = SINGLE_DISK_KS_SPACES