Don't remove leading or trailing IFS for passwords

[dereks_lifeofadishwasher.com]

Summary

PR: 245342

When entering a password sh's IFS default value (space tab, newline) so
any leading a trailing IFS characters are removed.

Setting IFS= (null) for just the two adduser.sh read lines will not
remove leading or trailing IFS characters.

Test Plan

(cmd)$ IFS= read -r p 	# with leading and trailing tabs
            foo 
(cmd)$ echo "|${p}|"
|           foo         |
(cmd)$ read -r p  	
            foo
(cmd)$ echo "|${p}|"
|foo|

(ins)$ IFS= read -r p  	# with leading and trailing space
   foo   
(cmd)$ echo "|${p}|"
|   foo   |
(cmd)$ read -r p
   foo   
(cmd)$ echo "|${p}|"
|foo|

Test adduser.sh with IFS= lines and su -l newuser with the space/tab.
Also, confirm the non-space/tab padded password doesn't work.

[jilles]

Some people wrongly add whitespace via copy and paste, but let's be consistent with login, passwd, etc.

[kevans]

Agreed; will commit this sometime today.