Use exec instead of exit $? in tests

Before this change, the shell process will linger around to extract the
exit value, only to return it to the parent process, and after
this change the task is left to the kernel and one less
process is used during testing.  This is a very small optimisation
of the tests to gut down the number of lines and reduce the resources
spend during testing.

Author: petterreinholdtsen

tests/hal-link-unlink/test.sh

@@ -3,6 +3,4 @@
 $REALTIME start
 python3 hallink.py
 
-$REALTIME stop
-
-exit $?
+exec $REALTIME stop

tests/halui/shared-test.sh

@@ -1,5 +1,4 @@
 #!/bin/bash
 
-linuxcnc -r halui.ini
-exit $?
+exec linuxcnc -r halui.ini
 

tests/interp/mdi-oword-m66/test.sh

@@ -1,5 +1,3 @@
 #!/bin/bash
 
-linuxcnc -r interp.ini
-exit $?
-
+exec linuxcnc -r interp.ini

tests/interp/oword-mdi-sub-update/test.sh

@@ -1,5 +1,3 @@
 #!/bin/bash
 
-linuxcnc -r interp.ini
-exit $?
-
+exec linuxcnc -r interp.ini

tests/interp/pymove/test.sh

@@ -1,3 +1,2 @@
 #!/bin/bash
-rs274 -i test.ini -n 0 -g test.ngc 2>&1
-exit $?
+exec rs274 -i test.ini -n 0 -g test.ngc 2>&1

tests/interp/python-self/test.sh

@@ -1,4 +1,3 @@
 #!/bin/bash
 export PYTHONUNBUFFERED=1
-rs274  -i test.ini -n 0 -g test.ngc 2>&1
-exit $?
+exec rs274  -i test.ini -n 0 -g test.ngc 2>&1

tests/interp/sequence-number/test.sh

@@ -1,3 +1,2 @@
 #!/bin/bash
-rs274 -n 0 -i test.ini -g test.ngc
-exit $?
+exec rs274 -n 0 -i test.ini -g test.ngc

tests/interp/subroutine-return/test.sh

@@ -3,6 +3,4 @@
 cp -f orig.ngc test.ngc
 cp -f subs/orig-sub.ngc subs/sub.ngc
 
-linuxcnc -r interp.ini
-exit $?
-
+exec linuxcnc -r interp.ini

tests/interp/value-returned/test.sh

@@ -1,3 +1,2 @@
 #!/bin/bash
-rs274 -i test.ini -n 0 -g test.ngc 2>&1
-exit $?
+exec rs274 -i test.ini -n 0 -g test.ngc 2>&1

tests/io-startup/shared-test.sh

@@ -3,6 +3,4 @@
 rm -f tool.tbl
 cp tool.tbl.original tool.tbl
 
-linuxcnc -r test.ini
-exit $?
-
+exec linuxcnc -r test.ini