Fix for double breakpoint (issue 4378296)

Fix for double breakpoint (issue 4378296)

Breakpoints are given special handling in the interpreter.  They
are first interpreted as a breakpoint (with notification to the
debugger), and then the actual instruction associated with the
breakpoint location is interpreted.

The bug here was that the "dvmCheckBefore()" handler was invoked
prior to both "interpretations" - rather than just the first.
Note that this defect appears only in the Arm mterp, the portable
interpreter and x86 mterp did the right thing.

Change-Id: Ied957edc0c248b5d4d94910beb7af6c03ffe885d