pldmd: add runtime switch to toggle debug logs

Currently the pldm daemon has a way to enable verbose logging via a
configure flag, however, a runtime verbose command line argument will
prove more helpful since that way the daemon can quickly be restarted to
enable/disable verbose logging without having to rebuild it.

Usage:
pldmd -v/--verbose $VERBOSE, where $VERBOSE has value 0 being for no
verbosity and 1 being full verbosity.
No option specified will have $VERBOSE value defaulted to 0.

Tested:
Without verbosity option (verbosity disabled by default)
root@witherspoon:/tmp# ./pldmd &
[1] 2274

With verbosity disabled
root@witherspoon:/tmp# ./pldmd --verbose 0 &
[1] 2275

With verbosity enabled
root@witherspoon:/tmp# ./pldmd --verbose 1 &
[1] 2276

with verbosity value error
root@witherspoon:/tmp# ./pldmd --verbose 3 &
[1] 2277
root@witherspoon:/tmp# Usage: ./pldmd [options]
Options:
  --verbose=<0/1>  0 - Disable verbosity, 1 - Enable verbosity

Signed-off-by: Jinu Joy Thomas <jinu.joy.thomas@in.ibm.com>
Change-Id: I48b1a0e919bc87f732e3c87f40225e0a63b727aa