ACCUMULO-2285 Default to MASTER1 if tracers or gc file is missing (1.4.x)

The start-all.sh script defaults to starting tracer and gc processes on the first
master if the tracers and gc files are missing from ACCUMULO_CONF_DIR. This change
adds that default behavior to stop-all.sh, which otherwise does not stop the
processes.
Merge branch '1.4.5-SNAPSHOT' into 1.5.1-SNAPSHOT (-sours)
Merge branch '1.5.1-SNAPSHOT' into 1.6.0-SNAPSHOT
Merge branch '1.6.0-SNAPSHOT'