adb: split up adb_auth.cpp.

All of the functions in adb_auth.cpp were used in only one of
adb/adbd. Split up them up into adb_auth_host.cpp and adbd_auth.cpp
respectively.

Bug: http://b/29273531
Test: built and flashed bullhead, adb still works
Change-Id: Ib610c5157522634cc273511175152f1306cc52a7
diff --git a/adb/Android.mk b/adb/Android.mk
index 0114ca3..b4e10fc 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -45,7 +45,6 @@
 # get enough of adb in here that we no longer need minadb. https://b/17626262
 LIBADB_SRC_FILES := \
     adb.cpp \
-    adb_auth.cpp \
     adb_io.cpp \
     adb_listeners.cpp \
     adb_trace.cpp \
@@ -103,7 +102,7 @@
 LOCAL_CFLAGS := $(LIBADB_CFLAGS) -DADB_HOST=0
 LOCAL_SRC_FILES := \
     $(LIBADB_SRC_FILES) \
-    adb_auth_client.cpp \
+    adbd_auth.cpp \
     jdwp_service.cpp \
     usb_linux_client.cpp \