Allow pool names that look like Solaris disk names

Nothing bad happens if a prefix of your pool name matches a disk name.
This is a bit of a silly restriction at this point.

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Ryan Moeller <freqlabs@FreeBSD.org>
Closes #11781 
Closes #11813

Author: Ryan Moeller

module/zcommon/zfs_namecheck.c

@@ -450,12 +450,6 @@ pool_namecheck(const char *pool, namecheck_err_t *why, char *what)
 		return (-1);
 	}
 
-	if (pool[0] == 'c' && (pool[1] >= '0' && pool[1] <= '9')) {
-		if (why)
-			*why = NAME_ERR_DISKLIKE;
-		return (-1);
-	}
-
 	return (0);
 }
 

tests/zfs-tests/tests/functional/pool_names/pool_names_002_neg.ksh

@@ -106,7 +106,7 @@ do
 done
 
 log_note "Verify invalid pool names fail"
-set -A POOLNAME "c0t0d0s0" "c0t0d0" "c0t0d19" "c0t50000E0108D279d0" \
+set -A POOLNAME \
     "mirror" "raidz" ",," ",,,,,,,,,,,,,,,,,,,,,,,,," \
     "2222222222222222222" "mirror_pool" "raidz_pool" \
     "mirror-pool" "raidz-pool" "spare" "spare_pool" \