tools: Fix use of continue

continue is not used in a proper context here (outside of loop). Use
null cmd instead to simply fall through the pip installation.

Signed-off-by: Michal Berger <michallinuxstuff@gmail.com>
Change-Id: Iaea2e5c0177b475edf19d08d71933a74debbb5d9
diff --git a/tools/install_pip.sh b/tools/install_pip.sh
index a80c178..c72dc89 100755
--- a/tools/install_pip.sh
+++ b/tools/install_pip.sh
@@ -128,7 +128,7 @@
     # if python3-pip is later installed.
     # For general sanity, we just use the packaged pip.  It should be
     # recent enough anyway.  This is included via rpms/general
-    continue
+    : # Simply fall through
 else
     install_get_pip
 fi