modify warning messages, avoid user confusion on Harmattan

modify warning messages, avoid user confusion on Harmattan

A lot of possible warnings during uninstallation are the result of (SHA1)
checksum mismatches. These have nothing to do with Harmattan's platform
security, which also happens to use SHA1 checksums for the very same purpose.
This could confuse users who have more advanced knowledge about Harmattan's
security internals.
Furthermore, it's irrelevant to the user how exactly busybox-power performs its
integrity checks.