JDWP: fix breakpoint on catch statement

Setting a breakpoint on a catch statement in the source actually
installs the breakpoint on a DEX move-exception instruction. At this
point, an exception is pending in the current thread.

The issue is no exception must be pending in the current thread to
report the breakpoint event. This is required to be able to call JNI
functions to create JDWP ids.

This CL fixes it by clearing the pending exception before reporting
event and restore it after reporting the event.

Bug: 21382373

(cherry picked from commit de48aa67)

Change-Id: Ie107eb47b6f2559c4fa5297f4033e07baad06f38