Feature/update to mbed os 5.8 (ARMmbed#109)

* change mbed os tag to mbed-os 5.8.4 and add new features to mbedignore
* Update update-client-hub to UC-R1.3.2-RC01
  Which include the following improvements
    * Use constant time binary compare function (IOTUC-308) (ARMmbed#217)
    * More robust update storage implementation (ARMmbed#221)

Author: LiyouZhou

.mbedignore

@@ -18,6 +18,9 @@ mbed-os/features/storage/*
 mbed-os/features/filesystem/littlefs/*
 mbed-os/features/filesystem/fat/*
 mbed-os/features/unsupported/*
+mbed-os/features/cellular/*
+mbed-os/features/lorawan/*
+mbed-os/features/nvstore/*
 update-client-hub/source/*
 update-client-hub/modules/atomic-queue/*
 update-client-hub/modules/control-center/*
@@ -55,4 +58,4 @@ mbed-client-esfs/Test/*
 mbed-client-esfs/Tools/*
 mbed-client-esfs/source/esfs.c
 mbed-client-esfs/source/esfs_file_name.c
-mbed-client-esfs/source/esfs_performance.c
+mbed-client-esfs/source/esfs_performance.c

mbed-os.lib

@@ -1 +1 @@
-https://github.com/ARMmbed/mbed-os/#eca67ca7dafab4ef70c21e2463b541132d0dd691
+https://github.com/ARMmbed/mbed-os/#ae6c7c60f91c89cbf755a2f3c8ec9c66635849fd

update-client-hub.lib

@@ -1 +1 @@
-https://github.com/ARMmbed/update-client-hub/#3f68620cb238c79095f5f91dfdd6fb212713b29b
+https://github.com/ARMmbed/update-client-hub/#2c359f09cc5fd4169e344242ad6da8b18efb241c