removeRdbFiles suffered from a confusion that ImplementationInfo.uri denotes the
corresponding component (.so, .jar, etc.), but not the .rdb file.  So removing
an .rdb file silently failed to remove the corresponding implementations, so re-
installing a similar enough .rdb (as typically happens during extension update)
would fail due to duplicate implementation names.

Change-Id: I25d4ff72656c99a3af509eef09e89c18cfd0aabe