fix mvno_match_data OutOfBounds Exception in substring check routine.

When the length of mvno_match_data is greater than GID from IccRecord,
It will generate StringIndexOutOfBoundsException.
Therefore, codes are changed to use startsWith() insteads of subString().

Change-Id: I04c5c5039edb2cfa757bf2f5a4b9f124afb69b06
Bugs: 10171336

Fix mvnoMatches function but keep case-insensitive

Redo previous fix in a way that's still case insensitive.

bug:10171336
Change-Id: I65e29b72ace2a41ed7a19e3bfb5d23bf3773d41c