Fix theoretical use of uninitialized values

Clang's static analyzer complains about this.

In get_configs(), if we have an invalid configuration that has no top
level vdevs, we can read a couple of uninitialized variables. Aborting
upon seeing this would break the userland tools for healthy pools, so we
instead initialize the two variables to 0 to allow the userland tools to
continue functioning for the pools with valid configurations.

In zfs_do_wait(), if no wait activities are enabled, we read an
uninitialized error variable.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes openzfs#14043

cmd/zfs/zfs_main.c

@@ -8554,7 +8554,7 @@ static int
 zfs_do_wait(int argc, char **argv)
 {
 	boolean_t enabled[ZFS_WAIT_NUM_ACTIVITIES];
-	int error, i;
+	int error = 0, i;
 	int c;
 
 	/* By default, wait for all types of activity. */

lib/libzutil/zutil_import.c

@@ -501,19 +501,18 @@ get_configs(libpc_handle_t *hdl, pool_list_t *pl, boolean_t active_ok,
 	uint64_t guid;
 	uint_t children = 0;
 	nvlist_t **child = NULL;
-	uint_t holes;
 	uint64_t *hole_array, max_id;
 	uint_t c;
 	boolean_t isactive;
-	uint64_t hostid;
 	nvlist_t *nvl;
 	boolean_t valid_top_config = B_FALSE;
 
 	if (nvlist_alloc(&ret, 0, 0) != 0)
 		goto nomem;
 
 	for (pe = pl->pools; pe != NULL; pe = pe->pe_next) {
-		uint64_t id, max_txg = 0;
+		uint64_t id, max_txg = 0, hostid = 0;
+		uint_t holes = 0;
 
 		if (nvlist_alloc(&config, NV_UNIQUE_NAME, 0) != 0)
 			goto nomem;