nvlist leaked in zpool_find_config()

In `zpool_find_config()`, the `pools` nvlist is leaked.  Part of it (a
sub-nvlist) is returned in `*configp`, but the callers also leak that.

Additionally, in `zdb.c:main()`, the `searchdirs` is leaked.

The leaks were detected by ASAN (`configure --enable-asan`).

This commit resolves the leaks.

Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #11396

cmd/zdb/zdb.c

@@ -8429,6 +8429,11 @@ main(int argc, char **argv)
 		}
 	}
 
+	if (searchdirs != NULL) {
+		umem_free(searchdirs, nsearch * sizeof (char *));
+		searchdirs = NULL;
+	}
+
 	/*
 	 * import_checkpointed_state makes the assumption that the
 	 * target pool that we pass it is already part of the spa
@@ -8447,6 +8452,11 @@ main(int argc, char **argv)
 			target = checkpoint_target;
 	}
 
+	if (cfg != NULL) {
+		nvlist_free(cfg);
+		cfg = NULL;
+	}
+
 	if (target_pool != target)
 		free(target_pool);
 

cmd/zhack/zhack.c

@@ -150,6 +150,7 @@ zhack_import(char *target, boolean_t readonly)
 	zfeature_checks_disable = B_TRUE;
 	error = spa_import(target, config, props,
 	    (readonly ?  ZFS_IMPORT_SKIP_MMP : ZFS_IMPORT_NORMAL));
+	fnvlist_free(config);
 	zfeature_checks_disable = B_FALSE;
 	if (error == EEXIST)
 		error = 0;

cmd/ztest/ztest.c

@@ -7016,6 +7016,7 @@ ztest_import_impl(ztest_shared_t *zs)
 	VERIFY0(zpool_find_config(NULL, ztest_opts.zo_pool, &cfg, &args,
 	    &libzpool_config_ops));
 	VERIFY0(spa_import(ztest_opts.zo_pool, cfg, NULL, flags));
+	fnvlist_free(cfg);
 }
 
 /*