CA-129230: Output of SM is truncated in logs (by syslog)

Problem: If an exception other than SR.SRException was raised in
SRCommand.run(), it was only caught and logged into SMlog by LVHD.
All other SR drivers let it pass to xapi, which in turn truncated
the traceback / exception message, making it difficult to debug.

Fix: There is now a single, driver agnostic point inside
SRCommand.run() that logs all exceptions to SMlog. Traceback
is not truncated. NOTE: All individual lines are limited to 989
characters.

Signed-off-by: Kostas Ladopoulos <Konstantinos.Ladopoulos@citrix.com>
CA-129230: [UnitTest] Three Unit Tests regarding the fix

Signed-off-by: Kostas Ladopoulos <Konstantinos.Ladopoulos@citrix.com>