[autotest] Change apk force install to default to True

This is to help to reduce flakes from adb install.

BUG=b:28382692
TEST=None

Change-Id: I3e4f672209cff24eed9c34ab54a4947e1f668ebe
Reviewed-on: https://chromium-review.googlesource.com/340537
Commit-Ready: Kris Rambish <krisr@chromium.org>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Kris Rambish <krisr@chromium.org>
diff --git a/server/hosts/adb_host.py b/server/hosts/adb_host.py
index 05fc90e..873b911 100644
--- a/server/hosts/adb_host.py
+++ b/server/hosts/adb_host.py
@@ -1371,7 +1371,7 @@
         return result.stdout.splitlines()
 
 
-    def install_apk(self, apk, force_reinstall=False):
+    def install_apk(self, apk, force_reinstall=True):
         """Install the specified apk.
 
         This will install the apk and override it if it's already installed and
@@ -1379,7 +1379,7 @@
 
         @param apk: The path to apk file.
         @param force_reinstall: True to reinstall the apk even if it's already
-                installed. Default is set to False.
+                installed. Default is set to True.
 
         @returns a CMDResult object.
         """