Add external/rootdev to the manifest.

BUG: 22953719

default.xml

@@ -264,6 +264,7 @@
   <project path="external/regex-re2" name="platform/external/regex-re2" groups="pdk-cw-fs,pdk-fs" />
   <project path="external/replicaisland" name="platform/external/replicaisland" groups="pdk-cw-fs,pdk-fs" />
   <project path="external/robolectric" name="platform/external/robolectric" groups="pdk-cw-fs,pdk-fs" />
+  <project path="external/rootdev" name="platform/external/rootdev" />
   <project path="external/safe-iop" name="platform/external/safe-iop" groups="pdk" />
   <project path="external/scrypt" name="platform/external/scrypt" groups="pdk" />
   <project path="external/selinux" name="platform/external/selinux" groups="pdk" />