Change "healthmonitor" to "health monitor" in help info

Change "healthmonitor" to "health monitor" in help info for the
following commands:
   lb-healthmonitor-create
   lb-healthmonitor-delete
   lb-healthmonitor-list
   lb-healthmonitor-show
   lb-healthmonitor-update

Change-Id: Icbb219d9e4a2d88e00c5734acc30b1c7609d02fc
Closes-Bug: 1377516
Merge "Change "healthmonitor" to "health monitor" in help info"