tests: explain why MD tests with metadata v0.90 are KNOWN-FAIL

metadata v0.90 is deprecated thing and unsupported to create by some new
mdadm versions. It's possible to assemble this array (with
default_layout=1 on modprobe raid0), but impossible to create a new
one.

References: 4ae96cf77b
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1826251
Signed-off-by: Karel Zak <kzak@redhat.com>

tests/ts/blkid/md-raid0-whole

@@ -29,7 +29,8 @@ ts_skip_nonroot
 ts_check_losetup
 ts_check_prog "mdadm"
 
-TS_KNOWN_FAIL="yes"	# due to recent changes in mdadm
+# rhbz#182625: It can't create new raid0 with metadata 0.90 from mdadm-4.1
+TS_KNOWN_FAIL="yes"
 
 ts_log "Initialize devices"
 IMGNAME="${TS_OUTDIR}/${TS_TESTNAME}"

tests/ts/blkid/md-raid1-part

@@ -28,7 +28,8 @@ ts_check_test_command "$TS_CMD_BLKID"
 ts_skip_nonroot
 ts_check_prog "mdadm"
 
-TS_KNOWN_FAIL="yes"	# due to recent changes in mdadm
+# rhbz#182625: It can't create new raid0 with metadata 0.90 from mdadm-4.1
+TS_KNOWN_FAIL="yes"
 
 # set global variable TS_DEVICE
 ts_scsi_debug_init dev_size_mb=51 sector_size=512

tests/ts/blkid/md-raid1-whole

@@ -29,7 +29,8 @@ ts_skip_nonroot
 ts_check_losetup
 ts_check_prog "mdadm"
 
-TS_KNOWN_FAIL="yes"	# due to recent changes in mdadm
+# rhbz#182625: It can't create new raid0 with metadata 0.90 from mdadm-4.1
+TS_KNOWN_FAIL="yes"
 
 ts_log "Initialize devices"
 IMGNAME="${TS_OUTDIR}/${TS_TESTNAME}"

tests/ts/fdisk/align-512-4K-md

@@ -31,7 +31,8 @@ ts_check_test_command "$TS_CMD_FDISK"
 ts_skip_nonroot
 ts_check_prog "mdadm"
 
-TS_KNOWN_FAIL="yes"	# due to recent changes in mdadm
+# rhbz#182625: It can't create new raid0 with metadata 0.90 from mdadm-4.1
+TS_KNOWN_FAIL="yes"
 
 # set global variable TS_DEVICE
 ts_scsi_debug_init dev_size_mb=50 sector_size=512 physblk_exp=3