[base-files] shell-scripting: fix wrong usage of '==' operator

normally the '==' is used for invoking a regex parser and is a bashism.
all of the fixes just want to compare a string. the used busybox-ash
will silently "ignore" this mistake, but make it portable/clean at least.

this patch does not change the behavior/logic of the scripts.

Signed-off-by: Bastian Bittorf <bittorf@bluebottle.com>

SVN-Revision: 42911