Add synchronization locks to shared objects

Make methods that read/write mBugreportInfos lock protected and add
"Locked" suffix to the method name. BugreportInfo objects are read/write
in different functions, to keep the code clean, add lock protected
getter/setter methods.

Bug: 142217059
Test: Takes interactive/full bugreports as expected
Change-Id: Iaadd6c9dce5009e40dd015e3b62bcd6e36966e00