The preferred way to set a user defined 'vars' file is to use global
option '--vars=<vars-file>'. Therefore, the current code erronously
does not check for externally set 'EASYRSA_VARS_FILE'.
This change now looks for a user defined 'vars' file by checking if
'EASYRSA_VARS_FILE' is defined, instead of 'user_vars_true'.
Also, move other automated 'vars' file locating to after the check
for user defined 'vars'.
Wrap long lines in set_var().
Signed-off-by: Richard T Bonhomme <tincantech@protonmail.com>