logging.bbclass: Enclose the tr string in quotes

On some linux hosts image recipes will fail to build as follows:

ERROR: build-essential-0.3-r0 do_image_ext3: Usage: bbdebug [123] "message"
ERROR: build-essential-0.3-r0 do_image_ext3: Function failed: do_image_ext3 (log file is located at /opt/build/tmp/work/intel_corei7_64-wrs-linux/build-essential/0.3-r0/temp/log.do_image_ext3.43744)
ERROR: Logfile of failure stored in: /opt/build/tmp/work/intel_corei7_64-wrs-linux/build-essential/0.3-r0/temp/log.do_image_ext3.43744
ERROR: Task (/opt/layers/meta-overc/meta-build/recipes-core/images/build-essential_0.3.bb:do_image_ext3) failed with exit code '1'

Running with bitbake -v -v -v -D we get in the log file:
+ bbdebug 1 Executing 'dd if=/dev/zero of=/opt/build/tmp/work/intel_corei7_64-wrs-linux/build-essential/0.3-r0/deploy-build-essential-image-complete/build-essential-intel-corei7-64-20180220190510.rootfs.ext3 seek=484486 count=0 bs=1024'
+ USAGE='Usage: bbdebug [123] "message"'
+ '[' 3 -lt 2 ']'
+ DBGLVL=1
+ shift
++ echo 1

++ echo 1
++ tr -d t

++ tr -d t
+ NONDIGITS=1
+ '[' 1 ']'
+ bbfatal 'Usage: bbdebug [123] "message"'

The debug output tells us that the NONDIGITS check failed to remove
the digits using the tr expression.  Enclosing the expression in
quotes causes it to work properly.

(From OE-Core rev: 9e6d283aa9c77685f55a62fa220226d9149ecd7a)

(From OE-Core rev: 35ed47d1fcbdd384aa804b686e1c92d22b74fc15)

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/logging.bbclass

@@ -86,7 +86,7 @@ bbdebug() {
 	
 	# Strip off the debug level and ensure it is an integer
 	DBGLVL=$1; shift
-	NONDIGITS=$(echo "$DBGLVL" | tr -d [:digit:])
+	NONDIGITS=$(echo "$DBGLVL" | tr -d "[:digit:]")
 	if [ "$NONDIGITS" ]; then
 		bbfatal "$USAGE"
 	fi