Fix import_path circular dependency by splitting it out.

Use import thread_pool instead from, from is evil.

Fix poweroff.out path for ./trace-boot.

test-boot

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 import common
+import lkmc.import_path
 import shell_helpers
 from shell_helpers import LF
 
@@ -45,7 +46,7 @@ See ./test --help for --size.
         #)
         #
         #rm -f "${self.env['test_boot_benchmark_file']}"
-        self.run = common.import_path_main('run')
+        self.run = lkmc.import_path.import_path_main('run')
         self.common_args = self.get_common_args()
         self.common_args['ctrl_c_host'] = True
         self.common_args['quit_after_boot'] = True