Solution to Task 6.1.7 Note the order in which the locks are taken. Updated for mbed os 5.4

Fork of Task617Solution-mbedos54 by Stage-1 Students SoCEM

Revision:
6:d16ce38e9b8a
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Mon Apr 03 11:38:04 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#50b3418e45484ebf442b88cd935a2d5355402d7d