check: source common/rc again if TEST_DEV was recreated

If TEST_DEV is recreated by check, FSTYP derived from TEST_DEV previously could be changed too and might not reflect the reality. So source common/rc again with correct FSTYP to get fs-specific configs, e.g. common/xfs.

For example, using this config-section config file, and run section ext4 first then xfs, you can see:

our local _scratch_mkfs routine ...
./common/rc: line 825: _scratch_mkfs_xfs: command not found
check: failed to mkfs $SCRATCH_DEV using specified options

local.config:
[default]
RECREATE_TEST_DEV=true
TEST_DEV=/dev/sda5
SCRATCH_DEV=/dev/sda6
TEST_DIR=/mnt/test
SCRATCH_MNT=/mnt/scratch

[ext4]
MKFS_OPTIONS="-b 4096"
FSTYP=ext4

[xfs]
FSTYP=xfs
MKFS_OPTIONS="-f -b size=4k"

---
 check | 4 ++++
 1 file changed, 4 insertions(+)

index f8db3cd6dfab..07586ce463c4 100755
@@ -555,6 +555,10 @@ for section in $HOST_OPTIONS_SECTIONS; do
 			status=1
 			exit
 		fi
+		# TEST_DEV has been recreated, previous FSTYP derived from
+		# TEST_DEV could be changed, source common/rc again with
+		# correct FSTYP to get FSTYP specific configs, e.g. common/xfs
+		. common/rc
 		_prepare_test_list
 	elif [ "$OLD_TEST_FS_MOUNT_OPTS" != "$TEST_FS_MOUNT_OPTS" ]; then
 		_test_unmount 2> /dev/null

2.14.3