tests: Add /sbin and /usr/sbin to path in partmap test

tests: Add /sbin and /usr/sbin to path in partmap test

The partmap test requires no elevated privileges. However, it uses parted
which can be used as a normal user, but is usually located in /sbin or
/usr/bin (eg. on Debian systems). Whereas the normal user does not usually
have /sbin or /usr/sbin added to their path, thus parted will not be found
causing the test to abort. Add /sbin and /usr/sbin to the path for the
partmap test so that the test can run successfully as an unprivileged user.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>