Remove optional alpha character at the end of the X-CS

Until we implement support for multiple ip ranges per carrier with different rules,
we allow several json configurations to refer to the same carrier.
Their X-CS ID will only differ by an extra letter appended to their ID, e.g. "250-99a"
In order for analytics to report correct stats, remove it before modifying X-Analytics.

Change-Id: If425dff13fe20b6a43897b54b24780eebc4c50dc