aa_status: Fix build issue with musl

Merged Armin kuster requested to merge akuster/apparmor:master into master

add limits.h

aa_status.c:269:22: error: 'PATH_MAX' undeclared (first use in this function); did you mean 'AF_MAX'? | 269 | real_exe = calloc(PATH_MAX + 1, sizeof(char));

Signed-off-by: Armin Kuster akuster808@gmail.com