iotests: Change coding style of _filter_nbd in 083

In order to be able to move _filter_nbd to common.filter in the next
patch, its coding style needs to be adapted to that of common.filter.
That means, we have to convert tabs to four spaces, adjust the alignment
of the last line (done with spaces already, assuming one tab equals
eight spaces), fix the line length of the comment, and add a line break
before the opening brace.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/083

@@ -49,15 +49,16 @@ wait_for_tcp_port() {
 	done
 }
 
-_filter_nbd() {
-	# nbd.c error messages contain function names and line numbers that are prone
-	# to change.  Message ordering depends on timing between send and receive
-	# callbacks sometimes, making them unreliable.
-	#
-	# Filter out the TCP port number since this changes between runs.
-	sed -e 's#^.*nbd/.*\.c:.*##g' \
-	    -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
-            -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
+_filter_nbd()
+{
+    # nbd.c error messages contain function names and line numbers that are
+    # prone to change.  Message ordering depends on timing between send and
+    # receive callbacks sometimes, making them unreliable.
+    #
+    # Filter out the TCP port number since this changes between runs.
+    sed -e 's#^.*nbd/.*\.c:.*##g' \
+        -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
+        -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
 }
 
 check_disconnect() {